diff --git a/tests/Makefile.am b/tests/Makefile.am
index 6d74333a..25da623b 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -1,6 +1,6 @@
 EXTRA_DIST = CMakeLists.txt main77.f main.f90
 
-AM_CPPFLAGS = -I$(top_srcdir)/src -I$(top_srcdir)/src/phreeqcpp -I$(top_srcdir)/src/phreeqcpp/PhreeqcKeywords
+AM_CPPFLAGS = -I$(top_srcdir)/src -I$(top_srcdir)/src/phreeqcpp -I$(top_srcdir)/src/phreeqcpp/common -I$(top_srcdir)/src/phreeqcpp/PhreeqcKeywords
 AM_FCFLAGS = -I$(top_srcdir)/src
 AM_FFLAGS = -I$(top_srcdir)/src