diff --git a/src/include/c.h b/src/include/c.h
index 9b7fe87f32..c38ef8aed3 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -36,9 +36,10 @@
  *		8)		random stuff
  *		9)		system-specific hacks
  *
- * NOTE: since this file is included by both frontend and backend modules, it's
- * almost certainly wrong to put an "extern" declaration here.  typedefs and
- * macros are the kind of thing that might go here.
+ * NOTE: since this file is included by both frontend and backend modules,
+ * it's usually wrong to put an "extern" declaration here, unless it's
+ * ifdef'd so that it's seen in only one case or the other.
+ * typedefs and macros are the kind of thing that might go here.
  *
  *----------------------------------------------------------------
  */
@@ -747,6 +748,18 @@ typedef NameData *Name;
 
 #endif							/* USE_ASSERT_CHECKING && !FRONTEND */
 
+/*
+ * ExceptionalCondition is compiled into the backend whether or not
+ * USE_ASSERT_CHECKING is defined, so as to support use of extensions
+ * that are built with that #define with a backend that isn't.  Hence,
+ * we should declare it as long as !FRONTEND.
+ */
+#ifndef FRONTEND
+extern void ExceptionalCondition(const char *conditionName,
+					 const char *errorType,
+					 const char *fileName, int lineNumber) pg_attribute_noreturn();
+#endif
+
 /*
  * Macros to support compile-time assertion checks.
  *
diff --git a/src/include/postgres.h b/src/include/postgres.h
index 3dc62801aa..bbcb50e41f 100644
--- a/src/include/postgres.h
+++ b/src/include/postgres.h
@@ -25,7 +25,6 @@
  *	  -------	------------------------------------------------
  *		1)		variable-length datatypes (TOAST support)
  *		2)		Datum type + support macros
- *		3)		exception handling backend support
  *
  *	 NOTES
  *
@@ -766,19 +765,4 @@ extern Datum Float8GetDatum(float8 X);
 #define Float4GetDatumFast(X) PointerGetDatum(&(X))
 #endif
 
-
-/* ----------------------------------------------------------------
- *				Section 3:	exception handling backend support
- * ----------------------------------------------------------------
- */
-
-/*
- * Backend only infrastructure for the assertion-related macros in c.h.
- *
- * ExceptionalCondition must be present even when assertions are not enabled.
- */
-extern void ExceptionalCondition(const char *conditionName,
-					 const char *errorType,
-					 const char *fileName, int lineNumber) pg_attribute_noreturn();
-
 #endif							/* POSTGRES_H */