Index: lib/Object/WasmObjectFile.cpp
===================================================================
--- lib/Object/WasmObjectFile.cpp
+++ lib/Object/WasmObjectFile.cpp
@@ -509,7 +509,7 @@
 
 Error WasmObjectFile::parseStartSection(const uint8_t *Ptr, const uint8_t *End) {
   StartFunction = readVaruint32(Ptr);
-  if (StartFunction < FunctionTypes.size())
+  if (StartFunction >= FunctionTypes.size())
     return make_error<GenericBinaryError>("Invalid start function",
                                           object_error::parse_failed);
   return Error::success();
Index: test/Object/wasm-invalid-start.test
===================================================================
--- /dev/null
+++ test/Object/wasm-invalid-start.test
@@ -0,0 +1,10 @@
+# RUN: yaml2obj %s | not llvm-objdump -h - 2>&1 | FileCheck %s
+
+!WASM
+FileHeader:
+  Version:         0x00000001
+Sections:
+  - Type:            START
+    StartFunction:   0
+
+# CHECK: {{.*}}: Invalid start function
Index: test/ObjectYAML/wasm/function_section.yaml
===================================================================
--- test/ObjectYAML/wasm/function_section.yaml
+++ test/ObjectYAML/wasm/function_section.yaml
@@ -4,9 +4,7 @@
   Version:         0x00000001
 Sections:
   - Type:            FUNCTION
-    FunctionTypes:   
-      - 1
-      - 0
+    FunctionTypes: [ 1, 0 ]
 ...
 # CHECK: --- !WASM
 # CHECK: FileHeader:
Index: test/ObjectYAML/wasm/start_section.yaml
===================================================================
--- test/ObjectYAML/wasm/start_section.yaml
+++ test/ObjectYAML/wasm/start_section.yaml
@@ -1,8 +1,17 @@
 # RUN: yaml2obj %s | obj2yaml | FileCheck %s
+
 --- !WASM
 FileHeader:
   Version:         0x00000001
 Sections:
+  - Type:            TYPE
+    Signatures:
+      - ReturnType:      I32
+        ParamTypes:
+          - F32
+          - F32
+  - Type:            FUNCTION
+    FunctionTypes: [ 0, 0, 0 ]
   - Type:            START
     StartFunction:   1
 ...