diff --git a/p4_constraints/BUILD.bazel b/p4_constraints/BUILD.bazel
index 79ef3c3..6aebb04 100644
--- a/p4_constraints/BUILD.bazel
+++ b/p4_constraints/BUILD.bazel
@@ -65,6 +65,7 @@ cc_library(
         ":constraint_source",
         "//gutils:proto",
         "//gutils:status",
+        "@com_google_absl//absl/log",
         "@com_google_absl//absl/status:statusor",
         "@com_google_absl//absl/strings",
         "@com_google_absl//absl/strings:str_format",
diff --git a/p4_constraints/ast.proto b/p4_constraints/ast.proto
index 3020fca..90a250a 100644
--- a/p4_constraints/ast.proto
+++ b/p4_constraints/ast.proto
@@ -36,7 +36,7 @@ message Expression {
     string integer_constant = 5;
     // A table key (aka "match field"), e.g. `header.ethernet.ether_type`.
     string key = 6;
-    // An action parameter.
+    // An action parameter name.
     string action_parameter = 13;
     Expression boolean_negation = 7;
     Expression arithmetic_negation = 8;
diff --git a/p4_constraints/quote.cc b/p4_constraints/quote.cc
index c6e7751..bdc0c32 100644
--- a/p4_constraints/quote.cc
+++ b/p4_constraints/quote.cc
@@ -17,6 +17,7 @@
 #include <sstream>
 #include <string>
 
+#include "absl/log/log.h"
 #include "absl/status/statusor.h"
 #include "absl/strings/str_cat.h"
 #include "absl/strings/str_format.h"
@@ -152,9 +153,13 @@ std::string GetSourceName(const ast::SourceLocation& source) {
       return source.table_name();
     case ast::SourceLocation::kFilePath:
       return source.file_path();
-    default:
-      return "Unknown Source Type";
+    case ast::SourceLocation::kActionName:
+      return source.action_name();
+    case ast::SourceLocation::SOURCE_NOT_SET:
+      break;
   }
+  LOG(DFATAL) << "Invalid Type: " << source.DebugString();
+  return "Unknown Source Type";
 }
 
 absl::StatusOr<std::string> QuoteSubConstraint(