--- Cbc/src/CbcSolver.cpp
+++ Cbc/src/CbcSolver.cpp
@@ -970,8 +970,13 @@
   this set of calls thread-safe.
 */
 
+#if defined _MSC_VER
 int CbcOrClpRead_mode = 1;
 FILE * CbcOrClpReadCommand = stdin;
+#else
+extern int CbcOrClpRead_mode;
+extern FILE * CbcOrClpReadCommand;
+#endif
 extern int CbcOrClpEnvironmentIndex;
 
 int callCbc1(const char * input2, CbcModel & model,
--- Clp/src/CbcOrClpParam.cpp
+++ Clp/src/CbcOrClpParam.cpp
@@ -1233,7 +1233,11 @@
 static char line[1000];
 static char * where = NULL;
 extern int CbcOrClpRead_mode;
+#if defined _MSC_VER || !defined COIN_HAS_CBC
 int CbcOrClpEnvironmentIndex = -1;
+#else
+extern int CbcOrClpEnvironmentIndex;
+#endif
 static size_t fillEnv()
 {
 #if defined(_MSC_VER) || defined(__MSVCRT__)