diff --git a/components/compiler/exprparser.cpp b/components/compiler/exprparser.cpp
index 319bb4498..07f576006 100644
--- a/components/compiler/exprparser.cpp
+++ b/components/compiler/exprparser.cpp
@@ -397,8 +397,15 @@ namespace Compiler
                     char returnType;
                     std::string argumentType;
 
-                    if (extensions->isFunction (keyword, returnType, argumentType, true))
+                    bool hasExplicit = true;
+                    if (extensions->isFunction (keyword, returnType, argumentType, hasExplicit))
                     {
+                        if (!hasExplicit)
+                        {
+                            getErrorHandler().warning ("stray explicit reference (ignoring it)", loc);
+                            mExplicit.clear();
+                        }
+
                         start();
 
                         mTokenLoc = loc;
@@ -519,7 +526,9 @@ namespace Compiler
                     char returnType;
                     std::string argumentType;
 
-                    if (extensions->isFunction (keyword, returnType, argumentType, false))
+                    bool hasExplicit = false;
+
+                    if (extensions->isFunction (keyword, returnType, argumentType, hasExplicit))
                     {
                         mTokenLoc = loc;
                         int optionals = parseArguments (argumentType, scanner);
diff --git a/components/compiler/extensions.cpp b/components/compiler/extensions.cpp
index 6f5c2fc89..c09abcbaf 100644
--- a/components/compiler/extensions.cpp
+++ b/components/compiler/extensions.cpp
@@ -22,7 +22,7 @@ namespace Compiler
     }
 
     bool Extensions::isFunction (int keyword, char& returnType, std::string& argumentType,
-        bool explicitReference) const
+        bool& explicitReference) const
     {
         std::map<int, Function>::const_iterator iter = mFunctions.find (keyword);
 
@@ -30,7 +30,7 @@ namespace Compiler
             return false;
 
         if (explicitReference && iter->second.mCodeExplicit==-1)
-            return false;
+            explicitReference = false;
 
         returnType = iter->second.mReturn;
         argumentType = iter->second.mArguments;
diff --git a/components/compiler/extensions.hpp b/components/compiler/extensions.hpp
index 585c42681..79cfed9e8 100644
--- a/components/compiler/extensions.hpp
+++ b/components/compiler/extensions.hpp
@@ -47,9 +47,11 @@ namespace Compiler
             /// - keyword must be all lower case.
 
             bool isFunction (int keyword, char& returnType, std::string& argumentType,
-                bool explicitReference) const;
+                bool& explicitReference) const;
             ///< Is this keyword registered with a function? If yes, return return and argument
             /// types.
+            /// \param explicitReference In: has explicit reference; Out: set to false, if
+            /// explicit reference is not available for this instruction.
 
             bool isInstruction (int keyword, std::string& argumentType,
                 bool& explicitReference) const;
diff --git a/components/compiler/lineparser.cpp b/components/compiler/lineparser.cpp
index 1407d0e95..e435b936c 100644
--- a/components/compiler/lineparser.cpp
+++ b/components/compiler/lineparser.cpp
@@ -279,9 +279,16 @@ namespace Compiler
                     char returnType;
                     std::string argumentType;
 
-                    if (extensions->isFunction (keyword, returnType, argumentType,
-                        !mExplicit.empty()))
+                    bool hasExplicit = !mExplicit.empty();
+
+                    if (extensions->isFunction (keyword, returnType, argumentType, hasExplicit))
                     {
+                        if (!hasExplicit && !mExplicit.empty())
+                        {
+                            getErrorHandler().warning ("stray explicit reference (ignoring it)", loc);
+                            mExplicit.clear();
+                        }
+
                         scanner.putbackKeyword (keyword, loc);
                         parseExpression (scanner, loc);
                         mState = EndState;