diff --git a/documentation/RELEASE_NOTES.html b/documentation/RELEASE_NOTES.html
index 6d686e3ed..363c8d605 100644
--- a/documentation/RELEASE_NOTES.html
+++ b/documentation/RELEASE_NOTES.html
@@ -15,9 +15,18 @@ EPICS Base 3.15.0.x releases are not intended for use in production systems.</p>
 <h2 align="center">Changes between 3.15.0.1 and 3.15.0.2</h2>
 <!-- Insert new items immediately below here ... -->
 
+<h3>Added macro EPICS_UNUSED to compilerDependencies.h</h3>
+
+<p>To prevent the compiler from warning about a known-unused variable, mark it
+with the macro EPICS_UNUSED. On gcc and clang this will expand to
+<tt>__attribute__((unused))</tt> to prevent the warning.</p>
+
 <h3>User specified db substitution file suffix</h3>
 
-<p>Per Dirk Zimoch's suggestion, a user specified db substitution file suffix is now allowed by setting the variable SUBST_SUFFIX in a configuration directory CONFIG_SITE file or in a Makefile before the include $(TOP)/configure/RULES line. The default is SUBST_SUFFIX=.substitutions.</p>
+<p>Per Dirk Zimoch's suggestion, a user specified db substitution file suffix is
+now allowed by setting the variable SUBST_SUFFIX in a configuration directory
+CONFIG_SITE file or in a Makefile before the include $(TOP)/configure/RULES
+line. The default for SUBST_SUFFIX is <tt>.substitutions</tt></p>
 
 <h3>NTP Time Provider adjusts to OS tick rate changes</h3>
 
diff --git a/src/libCom/osi/compiler/clang/compilerSpecific.h b/src/libCom/osi/compiler/clang/compilerSpecific.h
index 9c6b237c5..482ee513e 100644
--- a/src/libCom/osi/compiler/clang/compilerSpecific.h
+++ b/src/libCom/osi/compiler/clang/compilerSpecific.h
@@ -45,5 +45,9 @@
  */
 #define EPICS_DEPRECATED __attribute__((deprecated))
 
+/*
+ * Unused marker
+ */
+#define EPICS_UNUSED __attribute__((unused))
 
 #endif  /* ifndef compilerSpecific_h */
diff --git a/src/libCom/osi/compiler/gcc/compilerSpecific.h b/src/libCom/osi/compiler/gcc/compilerSpecific.h
index efd17e4b2..6696c7a89 100644
--- a/src/libCom/osi/compiler/gcc/compilerSpecific.h
+++ b/src/libCom/osi/compiler/gcc/compilerSpecific.h
@@ -60,5 +60,9 @@
 #   define EPICS_DEPRECATED __attribute__((deprecated))
 #endif
 
+/*
+ * Unused marker
+ */
+#define EPICS_UNUSED __attribute__((unused))
 
 #endif  /* ifndef compilerSpecific_h */
diff --git a/src/libCom/osi/compilerDependencies.h b/src/libCom/osi/compilerDependencies.h
index c91133996..bb077fbf0 100644
--- a/src/libCom/osi/compilerDependencies.h
+++ b/src/libCom/osi/compilerDependencies.h
@@ -58,5 +58,8 @@
 #define EPICS_DEPRECATED
 #endif
 
+#ifndef EPICS_UNUSED
+#   define EPICS_UNUSED
+#endif
 
 #endif  /* ifndef compilerDependencies_h */
diff --git a/src/libCom/osi/epicsAssert.h b/src/libCom/osi/epicsAssert.h
index db071d6cb..a16c036ec 100644
--- a/src/libCom/osi/epicsAssert.h
+++ b/src/libCom/osi/epicsAssert.h
@@ -18,6 +18,7 @@
 #define INC_epicsAssert_H
 
 #include "shareLib.h"
+#include "compilerDependencies.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -48,7 +49,7 @@ epicsShareFunc void epicsAssert (const char *pFile, const unsigned line,
 #define STATIC_JOIN2(x, y) x ## y
 #define STATIC_ASSERT(expr) \
     typedef int STATIC_JOIN(static_assert_failed_at_line_, __LINE__) \
-    [ (expr) ? 1 : -1 ]
+    [ (expr) ? 1 : -1 ] EPICS_UNUSED
 
 
 #ifdef __cplusplus