diff --git a/src/libCom/env/envDefs.h b/src/libCom/env/envDefs.h
index ac6132541..20f0eb2ad 100644
--- a/src/libCom/env/envDefs.h
+++ b/src/libCom/env/envDefs.h
@@ -95,6 +95,7 @@ epicsShareFunc long epicsShareAPI
     envGetBoolConfigParam(const ENV_PARAM *pParam, int *pBool);
 epicsShareFunc long epicsShareAPI epicsPrtEnvParams(void);
 epicsShareFunc void epicsShareAPI epicsEnvSet (const char *name, const char *value);
+epicsShareFunc void epicsShareAPI epicsEnvUnset (const char *name);
 epicsShareFunc void epicsShareAPI epicsEnvShow (const char *name);
 
 #ifdef __cplusplus