diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/lvalues/as-expression/input.js b/packages/babel-plugin-transform-typescript/test/fixtures/lvalues/as-expression/input.js
new file mode 100644
index 0000000000..595ffcebf8
--- /dev/null
+++ b/packages/babel-plugin-transform-typescript/test/fixtures/lvalues/as-expression/input.js
@@ -0,0 +1 @@
+(x as number) += 1;
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/lvalues/as-expression/output.js b/packages/babel-plugin-transform-typescript/test/fixtures/lvalues/as-expression/output.js
new file mode 100644
index 0000000000..7150d6e7aa
--- /dev/null
+++ b/packages/babel-plugin-transform-typescript/test/fixtures/lvalues/as-expression/output.js
@@ -0,0 +1 @@
+x += 1;
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/lvalues/non-null/input.js b/packages/babel-plugin-transform-typescript/test/fixtures/lvalues/non-null/input.js
new file mode 100644
index 0000000000..da07f8efdb
--- /dev/null
+++ b/packages/babel-plugin-transform-typescript/test/fixtures/lvalues/non-null/input.js
@@ -0,0 +1 @@
+x! += 1;
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/lvalues/non-null/output.js b/packages/babel-plugin-transform-typescript/test/fixtures/lvalues/non-null/output.js
new file mode 100644
index 0000000000..7150d6e7aa
--- /dev/null
+++ b/packages/babel-plugin-transform-typescript/test/fixtures/lvalues/non-null/output.js
@@ -0,0 +1 @@
+x += 1;
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/lvalues/type-assertion/input.js b/packages/babel-plugin-transform-typescript/test/fixtures/lvalues/type-assertion/input.js
new file mode 100644
index 0000000000..25af225794
--- /dev/null
+++ b/packages/babel-plugin-transform-typescript/test/fixtures/lvalues/type-assertion/input.js
@@ -0,0 +1 @@
+(<number> x) += 1;
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/lvalues/type-assertion/output.js b/packages/babel-plugin-transform-typescript/test/fixtures/lvalues/type-assertion/output.js
new file mode 100644
index 0000000000..7150d6e7aa
--- /dev/null
+++ b/packages/babel-plugin-transform-typescript/test/fixtures/lvalues/type-assertion/output.js
@@ -0,0 +1 @@
+x += 1;
diff --git a/packages/babylon/src/plugins/typescript.js b/packages/babylon/src/plugins/typescript.js
index f1473c5d72..e5494e92bd 100644
--- a/packages/babylon/src/plugins/typescript.js
+++ b/packages/babylon/src/plugins/typescript.js
@@ -1941,6 +1941,8 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         case "TSParameterProperty":
           return super.toAssignable(node, isBinding, contextDescription);
         case "TSAsExpression":
+        case "TSNonNullExpression":
+        case "TSTypeAssertion":
           node.expression = this.toAssignable(
             node.expression,
             isBinding,
@@ -1973,6 +1975,8 @@ export default (superClass: Class<Parser>): Class<Parser> =>
           );
           return;
         case "TSAsExpression":
+        case "TSNonNullExpression":
+        case "TSTypeAssertion":
           this.checkLVal(
             expr.expression,
             isBinding,
diff --git a/packages/babylon/test/fixtures/typescript/cast/null-assertion-and-assign/input.js b/packages/babylon/test/fixtures/typescript/cast/null-assertion-and-assign/input.js
new file mode 100644
index 0000000000..da07f8efdb
--- /dev/null
+++ b/packages/babylon/test/fixtures/typescript/cast/null-assertion-and-assign/input.js
@@ -0,0 +1 @@
+x! += 1;
diff --git a/packages/babylon/test/fixtures/typescript/cast/null-assertion-and-assign/output.json b/packages/babylon/test/fixtures/typescript/cast/null-assertion-and-assign/output.json
new file mode 100644
index 0000000000..01c14c609d
--- /dev/null
+++ b/packages/babylon/test/fixtures/typescript/cast/null-assertion-and-assign/output.json
@@ -0,0 +1,117 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 8,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 8
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 8,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 8
+      }
+    },
+    "sourceType": "module",
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start": 0,
+        "end": 8,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 8
+          }
+        },
+        "expression": {
+          "type": "AssignmentExpression",
+          "start": 0,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 0
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            }
+          },
+          "operator": "+=",
+          "left": {
+            "type": "TSNonNullExpression",
+            "start": 0,
+            "end": 2,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 0
+              },
+              "end": {
+                "line": 1,
+                "column": 2
+              }
+            },
+            "expression": {
+              "type": "Identifier",
+              "start": 0,
+              "end": 1,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 0
+                },
+                "end": {
+                  "line": 1,
+                  "column": 1
+                },
+                "identifierName": "x"
+              },
+              "name": "x"
+            }
+          },
+          "right": {
+            "type": "NumericLiteral",
+            "start": 6,
+            "end": 7,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 6
+              },
+              "end": {
+                "line": 1,
+                "column": 7
+              }
+            },
+            "extra": {
+              "rawValue": 1,
+              "raw": "1"
+            },
+            "value": 1
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}
diff --git a/packages/babylon/test/fixtures/typescript/cast/type-assertion-and-assign/input.js b/packages/babylon/test/fixtures/typescript/cast/type-assertion-and-assign/input.js
new file mode 100644
index 0000000000..25af225794
--- /dev/null
+++ b/packages/babylon/test/fixtures/typescript/cast/type-assertion-and-assign/input.js
@@ -0,0 +1 @@
+(<number> x) += 1;
diff --git a/packages/babylon/test/fixtures/typescript/cast/type-assertion-and-assign/output.json b/packages/babylon/test/fixtures/typescript/cast/type-assertion-and-assign/output.json
new file mode 100644
index 0000000000..944c081bdc
--- /dev/null
+++ b/packages/babylon/test/fixtures/typescript/cast/type-assertion-and-assign/output.json
@@ -0,0 +1,136 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 18,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 18
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 18,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 18
+      }
+    },
+    "sourceType": "module",
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start": 0,
+        "end": 18,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 18
+          }
+        },
+        "expression": {
+          "type": "AssignmentExpression",
+          "start": 0,
+          "end": 17,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 0
+            },
+            "end": {
+              "line": 1,
+              "column": 17
+            }
+          },
+          "operator": "+=",
+          "left": {
+            "type": "TSTypeAssertion",
+            "start": 2,
+            "end": 11,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 2
+              },
+              "end": {
+                "line": 1,
+                "column": 11
+              }
+            },
+            "expression": {
+              "type": "Identifier",
+              "start": 10,
+              "end": 11,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 10
+                },
+                "end": {
+                  "line": 1,
+                  "column": 11
+                },
+                "identifierName": "x"
+              },
+              "name": "x"
+            },
+            "typeAnnotation": {
+              "type": "TSNumberKeyword",
+              "start": 2,
+              "end": 8,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 2
+                },
+                "end": {
+                  "line": 1,
+                  "column": 8
+                }
+              }
+            },
+            "extra": {
+              "parenthesized": true,
+              "parenStart": 0
+            }
+          },
+          "right": {
+            "type": "NumericLiteral",
+            "start": 16,
+            "end": 17,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 16
+              },
+              "end": {
+                "line": 1,
+                "column": 17
+              }
+            },
+            "extra": {
+              "rawValue": 1,
+              "raw": "1"
+            },
+            "value": 1
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}