diff --git a/builtin/merge-tree.c b/builtin/merge-tree.c
index e72714a..de85207 100644
--- a/builtin/merge-tree.c
+++ b/builtin/merge-tree.c
@@ -109,6 +109,7 @@
 	xdemitconf_t xecfg;
 	xdemitcb_t ecb;
 
+	memset(&xpp, 0, sizeof(xpp));
 	xpp.flags = 0;
 	memset(&xecfg, 0, sizeof(xecfg));
 	xecfg.ctxlen = 3;
diff --git a/xdiff/xhistogram.c b/xdiff/xhistogram.c
index c7b35a9..e694bfd 100644
--- a/xdiff/xhistogram.c
+++ b/xdiff/xhistogram.c
@@ -235,6 +235,8 @@
 		int line1, int count1, int line2, int count2)
 {
 	xpparam_t xpparam;
+
+	memset(&xpparam, 0, sizeof(xpparam));
 	xpparam.flags = xpp->flags & ~XDF_DIFF_ALGORITHM_MASK;
 
 	return xdl_fall_back_diff(env, &xpparam,
diff --git a/xdiff/xpatience.c b/xdiff/xpatience.c
index 3c5601b..20699a6 100644
--- a/xdiff/xpatience.c
+++ b/xdiff/xpatience.c
@@ -318,6 +318,8 @@
 		int line1, int count1, int line2, int count2)
 {
 	xpparam_t xpp;
+
+	memset(&xpp, 0, sizeof(xpp));
 	xpp.flags = map->xpp->flags & ~XDF_DIFF_ALGORITHM_MASK;
 
 	return xdl_fall_back_diff(map->env, &xpp,