diff --git a/unit/GNUmakefile b/unit/GNUmakefile
index 36dc72fc..2603f5be 100644
--- a/unit/GNUmakefile
+++ b/unit/GNUmakefile
@@ -58,6 +58,7 @@ PPOBJS = \
 	dumper.o \
 	Exchange.o \
 	ExchComp.o \
+	GasComp.o \
 	GasPhase.o \
 	ISolutionComp.o \
 	ISolution.o \