diff --git a/configure.ac b/configure.ac
index 9af28e5a..9776c8cf 100644
--- a/configure.ac
+++ b/configure.ac
@@ -195,6 +195,7 @@ LIBS=""
 
 dnl check for some default libraries
 AC_SEARCH_LIBS(cos, m)
+AC_SEARCH_LIBS(clock_gettime, rt)
 
 base_LIBS="$LIBS"
 
diff --git a/src/Prep/Photo/Makefile.am b/src/Prep/Photo/Makefile.am
index 74bd6285..06f67e13 100644
--- a/src/Prep/Photo/Makefile.am
+++ b/src/Prep/Photo/Makefile.am
@@ -42,11 +42,11 @@ photo_LDADD = \
 
 wgs84offset_SOURCES = wgs84offset.cxx
 
-wgs84offset_LDADD = -lsgmath -lsgdebug
+wgs84offset_LDADD = -lsgmath -lsgdebug -lsgstructure
 
 findcorners_SOURCES = findcorners.cxx
 
-findcorners_LDADD = -lsgmath -lsgdebug
+findcorners_LDADD = -lsgmath -lsgdebug -lsgstructure
 
 INCLUDES = \
 	-I$(top_srcdir) \
diff --git a/src/Prep/UserDef/Makefile.am b/src/Prep/UserDef/Makefile.am
index ca0da508..988b940f 100644
--- a/src/Prep/UserDef/Makefile.am
+++ b/src/Prep/UserDef/Makefile.am
@@ -10,6 +10,7 @@ tguserdef_LDADD = \
 	$(top_builddir)/src/Lib/TriangleJRS/libTriangleJRS.a \
 	-lsgbucket -lsgmisc -lsgmath -lsgprops -lsgio -lsgstructure -lsgxml \
 	-lsgdebug \
+	-lOpenThreads \
 	-lgenpolyclip -lz
 
 INCLUDES = -I$(top_srcdir)/src/Lib