diff --git a/App/tools/driver.makefile b/App/tools/driver.makefile
index fb9c57d..06a10dd 100644
--- a/App/tools/driver.makefile
+++ b/App/tools/driver.makefile
@@ -486,7 +486,7 @@ else
 
 # Add sources for specific epics types (3.13 or 3.14) or architectures.
 ARCH_PARTS = ${T_A} $(subst -, ,${T_A}) ${OS_CLASS}
-VAR_EXTENSIONS = ${EPICS_BASETYPE} ${EPICSVERSION} ${ARCH_PARTS} ${ARCH_PARTS:%=${EPICS_BASETYPE}_%} ${ARCH_PARTS:%=${EPICSVERSION}_%}
+VAR_EXTENSIONS = $(firstword $(subst ., ,${EPICSVERSION})) ${EPICS_BASETYPE} ${EPICSVERSION} ${ARCH_PARTS} ${ARCH_PARTS:%=${EPICS_BASETYPE}_%} ${ARCH_PARTS:%=${EPICSVERSION}_%}
 export VAR_EXTENSIONS
 
 REQ = ${REQUIRED} $(foreach x, ${VAR_EXTENSIONS}, ${REQUIRED_$x})