diff --git a/lib/Differentiator/ReverseModeVisitor.cpp b/lib/Differentiator/ReverseModeVisitor.cpp
index d8d4b0cda..5d67f334e 100644
--- a/lib/Differentiator/ReverseModeVisitor.cpp
+++ b/lib/Differentiator/ReverseModeVisitor.cpp
@@ -2516,9 +2516,9 @@ Expr* getArraySizeExpr(const ArrayType* AT, ASTContext& context,
   VarDeclDiff ReverseModeVisitor::DifferentiateVarDecl(const VarDecl* VD) {
     StmtDiff initDiff;
     Expr* VDDerivedInit = nullptr;
-    // FIXME: find a more reliable way to determine if the declaration
-    // is in the function global scope.
-    bool isInFunctionGlobalScope = m_Reverse.size() <= 2;
+    // We take the parent of the current scope because the main compound
+    // statement of the function has its own scope as well.
+    bool isInFunctionGlobalScope = getCurrentScope()->getParent()==m_DerivativeFnScope;
     auto VDDerivedType = ComputeAdjointType(VD->getType());
     auto VDCloneType = CloneType(VD->getType());
     if (!isInFunctionGlobalScope)
@@ -2725,9 +2725,9 @@ Expr* getArraySizeExpr(const ArrayType* AT, ASTContext& context,
     llvm::SmallVector<Decl*, 4> declsDiff;
     // Need to put array decls inlined.
     llvm::SmallVector<Decl*, 4> localDeclsDiff;
-    // FIXME: find a more reliable way to determine if the declaration
-    // is in the function global scope.
-    bool isInFunctionGlobalScope = m_Reverse.size() <= 2;
+    // We take the parent of the current scope because the main compound
+    // statement of the function has its own scope as well.
+    bool isInFunctionGlobalScope = getCurrentScope()->getParent()==m_DerivativeFnScope;
     // For each variable declaration v, create another declaration _d_v to
     // store derivatives for potential reassignments. E.g.
     // double y = x;