diff --git a/Ghidra/Features/Decompiler/src/decompile/cpp/funcdata_varnode.cc b/Ghidra/Features/Decompiler/src/decompile/cpp/funcdata_varnode.cc
index 41fe8fed5e..a8e761ea19 100644
--- a/Ghidra/Features/Decompiler/src/decompile/cpp/funcdata_varnode.cc
+++ b/Ghidra/Features/Decompiler/src/decompile/cpp/funcdata_varnode.cc
@@ -1222,11 +1222,10 @@ bool Funcdata::attemptDynamicMapping(SymbolEntry *entry,DynamicHash &dhash)
   }
   Varnode *vn = dhash.findVarnode(this,entry->getFirstUseAddress(),entry->getHash());
   if (vn == (Varnode *)0) return false;
+  if (vn->getSymbolEntry() != (SymbolEntry *)0) return false;	// Varnode is already labeled
   if (category == Symbol::equate) {	// Is this an equate symbol
-    if (vn->mapentry != entry) {	// Check we haven't marked this before
-      vn->setSymbolEntry(entry);
-      return true;
-    }
+    vn->setSymbolEntry(entry);
+    return true;
   }
   else if (entry->getSize() == vn->getSize()) {
     if (vn->setSymbolProperties(entry))
@@ -1254,7 +1253,7 @@ bool Funcdata::attemptDynamicMappingLate(SymbolEntry *entry,DynamicHash &dhash)
   Varnode *vn = dhash.findVarnode(this,entry->getFirstUseAddress(),entry->getHash());
   if (vn == (Varnode *)0)
     return false;
-  if (vn->getSymbolEntry() == entry) return false; // Already applied it
+  if (vn->getSymbolEntry() != (SymbolEntry *)0) return false; // Symbol already applied
   if (sym->getCategory() == Symbol::equate) {	// Equate symbol does not depend on size
     vn->setSymbolEntry(entry);
     return true;
diff --git a/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/SpecExtension.java b/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/SpecExtension.java
index 0b2ee72704..01372bef38 100644
--- a/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/SpecExtension.java
+++ b/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/SpecExtension.java
@@ -637,7 +637,13 @@ public class SpecExtension {
 		}
 		cspecValidator.verify(res.optionName, document);
 		checkExtension(res);
-		parseExtension(res.optionName, document, program.getCompilerSpec(), false);
+		if (!(program.getCompilerSpec() instanceof BasicCompilerSpec)) {
+			throw new SleighException(
+				"Can only test specification extensions against SLEIGH program");
+		}
+		BasicCompilerSpec cSpecCopy =
+			new BasicCompilerSpec((BasicCompilerSpec) program.getCompilerSpec());
+		parseExtension(res.optionName, document, cSpecCopy, false);
 		return res;
 	}
 
diff --git a/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/lang/BasicCompilerSpec.java b/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/lang/BasicCompilerSpec.java
index 921d6d25a1..f340c80ee8 100644
--- a/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/lang/BasicCompilerSpec.java
+++ b/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/lang/BasicCompilerSpec.java
@@ -157,7 +157,7 @@ public class BasicCompilerSpec implements CompilerSpec {
 	 * spec from Language.
 	 * @param op2 is the spec to clone
 	 */
-	protected BasicCompilerSpec(BasicCompilerSpec op2) {
+	public BasicCompilerSpec(BasicCompilerSpec op2) {
 		language = op2.language;
 		description = op2.description;
 		// PrototypeModel is immutable but the map may change, so callingConventionMap