diff --git a/include/llvm/ExecutionEngine/RuntimeDyldChecker.h b/include/llvm/ExecutionEngine/RuntimeDyldChecker.h
index 38a4ea1ad52..8dd891e8364 100644
--- a/include/llvm/ExecutionEngine/RuntimeDyldChecker.h
+++ b/include/llvm/ExecutionEngine/RuntimeDyldChecker.h
@@ -81,7 +81,7 @@ public:
 
 private:
 
-  bool checkSymbolIsValidForLoad(StringRef Symbol) const;
+  bool isSymbolValid(StringRef Symbol) const;
   uint64_t getSymbolAddress(StringRef Symbol) const;
   uint64_t readMemoryAtSymbol(StringRef Symbol, int64_t Offset,
                               unsigned Size) const;
diff --git a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldChecker.cpp b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldChecker.cpp
index 190bbbf93ff..b10ec360aa5 100644
--- a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldChecker.cpp
+++ b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldChecker.cpp
@@ -199,7 +199,7 @@ namespace llvm {
       StringRef Symbol;
       std::tie(Symbol, RemainingExpr) = parseSymbol(RemainingExpr);
 
-      if (!Checker.checkSymbolIsValidForLoad(Symbol))
+      if (!Checker.isSymbolValid(Symbol))
         return std::make_pair(EvalResult(("Cannot decode unknown symbol '" +
                                           Symbol + "'").str()),
                               "");
@@ -268,7 +268,7 @@ namespace llvm {
       StringRef Symbol;
       std::tie(Symbol, RemainingExpr) = parseSymbol(RemainingExpr);
 
-      if (!Checker.checkSymbolIsValidForLoad(Symbol))
+      if (!Checker.isSymbolValid(Symbol))
         return std::make_pair(EvalResult(("Cannot decode unknown symbol '"
                                           + Symbol + "'").str()),
                               "");
@@ -304,6 +304,17 @@ namespace llvm {
       else if (Symbol == "next_pc")
         return evalNextPC(RemainingExpr);
 
+      if (!Checker.isSymbolValid(Symbol)) {
+        std::string ErrMsg("No known address for symbol '");
+        ErrMsg += Symbol;
+        ErrMsg += "'";
+        if (Symbol.startswith("L"))
+          ErrMsg += " (this appears to be an assembler local label - "
+                    " perhaps drop the 'L'?)";
+
+        return std::make_pair(EvalResult(ErrMsg), "");
+      }
+
       // Looks like a plain symbol reference.
       return std::make_pair(EvalResult(Checker.getSymbolAddress(Symbol)),
                             RemainingExpr);
@@ -397,7 +408,7 @@ namespace llvm {
       StringRef Symbol;
       std::tie(Symbol, RemainingExpr) = parseSymbol(RemainingExpr);
 
-      if (!Checker.checkSymbolIsValidForLoad(Symbol))
+      if (!Checker.isSymbolValid(Symbol))
         return std::make_pair(EvalResult(("Cannot dereference unknown symbol '"
                                           + Symbol + "'").str()),
                               "");
@@ -612,7 +623,7 @@ bool RuntimeDyldChecker::checkAllRulesInBuffer(StringRef RulePrefix,
   return DidAllTestsPass && (NumRules != 0);
 }
 
-bool RuntimeDyldChecker::checkSymbolIsValidForLoad(StringRef Symbol) const {
+bool RuntimeDyldChecker::isSymbolValid(StringRef Symbol) const {
   return RTDyld.getSymbolAddress(Symbol) != nullptr;
 }