diff --git a/package.json b/package.json
index 83810972..ae1a8002 100644
--- a/package.json
+++ b/package.json
@@ -85,4 +85,4 @@
     "strip-indent": "^2.0.0",
     "typescript": "^2.1.4"
   }
-}
\ No newline at end of file
+}
diff --git a/src/javascript/ast-value.ts b/src/javascript/ast-value.ts
index 941d3140..793db115 100644
--- a/src/javascript/ast-value.ts
+++ b/src/javascript/ast-value.ts
@@ -30,13 +30,13 @@ function unaryToValue(unary: estree.UnaryExpression): LiteralValue {
   const operand = expressionToValue(unary.argument);
   switch (unary.operator) {
     case '!':
-      return !operand;
+      return !(operand as any);
     case '-':
-      return -operand;
+      return -(operand as any);
     case '+':
-      return +operand;
+      return +(operand as any);
     case '~':
-      return ~operand;
+      return ~(operand as any);
     case 'typeof':
       return typeof operand;
     case 'void':
diff --git a/src/perf/parse-all-benchmark.ts b/src/perf/parse-all-benchmark.ts
index 1ed78833..92ebd08b 100644
--- a/src/perf/parse-all-benchmark.ts
+++ b/src/perf/parse-all-benchmark.ts
@@ -176,7 +176,7 @@ class Averager<K> {
 
   entries(): Iterable<[K, number]> {
     const entries = this.count.keys().map(
-        (k) => <[K, number]>[k, this.elapsed.get(k) / this.count.get(k)]);
+        (k) => <[K, number]>[k, this.elapsed.get(k)! / this.count.get(k)!]);
     return entries.sort((a, b) => a[1] - b[1]);
   }
 }
diff --git a/src/typescript/typescript-analyzer.ts b/src/typescript/typescript-analyzer.ts
index 657ce222..95d0c459 100644
--- a/src/typescript/typescript-analyzer.ts
+++ b/src/typescript/typescript-analyzer.ts
@@ -49,7 +49,7 @@ function isLibraryPath(filename: string) {
   return filename.startsWith('/$lib/');
 }
 
-const libraryCache = new Map<string, string>();
+const libraryCache = new Map<string, string|undefined>();
 function getLibrarySource(filePath: string) {
   if (libraryCache.has(filePath)) {
     return libraryCache.get(filePath);