diff --git a/src/engine/build.sh b/src/engine/build.sh
index 75a53e3f43..caa8e81f31 100755
--- a/src/engine/build.sh
+++ b/src/engine/build.sh
@@ -341,8 +341,8 @@ case "${B2_TOOLSET}" in
     ;;
 
     ibmcxx-clang)
-        CXX_VERSION_OPT=${CXX_VERSION_OPT:--qversion}
-        B2_CXXFLAGS_RELEASE="-O3 -s -Wno-deprecated-declarations"
+        CXX_VERSION_OPT=${CXX_VERSION_OPT:---version}
+        B2_CXXFLAGS_RELEASE="-O3 -Wl,-s -Wno-deprecated-declarations"
         B2_CXXFLAGS_DEBUG="-O0 -fno-inline -g -Wno-deprecated-declarations"
     ;;
 
diff --git a/src/engine/jam.h b/src/engine/jam.h
index c69895a873..61ccd16191 100644
--- a/src/engine/jam.h
+++ b/src/engine/jam.h
@@ -147,7 +147,9 @@
 #define PATH_DELIM '/'
 
 #ifdef _AIX
+    #ifndef unix
     #define unix
+    #endif
     #define MAXLINE 23552  /* 24k - 1k, max chars per command line */
     #define OSMINOR "OS=AIX"
     #define OS_AIX