diff --git a/src/secp256k1/src/modules/multiset/main_impl.h b/src/secp256k1/src/modules/multiset/main_impl.h
--- a/src/secp256k1/src/modules/multiset/main_impl.h
+++ b/src/secp256k1/src/modules/multiset/main_impl.h
@@ -106,6 +106,13 @@
     gej_from_multiset_var(&source, multiset);
     ge_from_data_var(&newelm, input, inputLen, remove);
 
+    /*
+     * The `target` group element needs to be initialized.
+     * If the result of the addition is infinity, the field elements won't be
+     * set and the `secp256k1_fe_normalize` calls below will branch on
+     * uninitialized data.
+     */
+    secp256k1_gej_set_infinity(&target);
     secp256k1_gej_add_ge_var(&target, &source, &newelm, NULL);
 
     secp256k1_fe_normalize(&target.x);
@@ -137,6 +144,13 @@
     gej_from_multiset_var(&gej_multiset, multiset);
     gej_from_multiset_var(&gej_input, input);
 
+    /*
+     * The `gej_result` group element needs to be initialized.
+     * If the result of the addition is infinity, the field elements won't be
+     * set and the `secp256k1_fe_normalize` calls below will branch on
+     * uninitialized data.
+     */
+    secp256k1_gej_set_infinity(&gej_result);
     secp256k1_gej_add_var(&gej_result, &gej_multiset, &gej_input, NULL);
 
     secp256k1_fe_normalize(&gej_result.x);
diff --git a/src/secp256k1/src/modules/multiset/tests_impl.h b/src/secp256k1/src/modules/multiset/tests_impl.h
--- a/src/secp256k1/src/modules/multiset/tests_impl.h
+++ b/src/secp256k1/src/modules/multiset/tests_impl.h
@@ -102,6 +102,7 @@
     /* Testing if combining is effectively the same as adding the elements */
 
     secp256k1_multiset empty, r1,r2,r3;
+    secp256k1_gej gej_pos, gej_neg;
 
     secp256k1_multiset_init(ctx, &empty);
     secp256k1_multiset_init(ctx, &r1);
@@ -144,6 +145,25 @@
     CHECK_EQUAL(&r1,&r2); /* M(0,1,2)+M() == M(0,1,2) */
     secp256k1_multiset_combine(ctx, &r2, &r1);
     CHECK_NOTEQUAL(&r1,&r2); /* M(0,1,2)+M(0,1,2) != M(0,1,2) */
+
+    /* Combine multisets so that the combination representation is infinity */
+    secp256k1_multiset_init(ctx, &r1);
+    secp256k1_multiset_init(ctx, &r2);
+    CHECK_EQUAL(&r1, &r2); /* M() == M() */
+
+    secp256k1_multiset_add(ctx, &r1, elements[0], DATALEN);
+
+    gej_from_multiset_var(&gej_pos, &r1);
+    secp256k1_gej_neg(&gej_neg, &gej_pos);
+    secp256k1_fe_normalize(&gej_neg.x);
+    secp256k1_fe_normalize(&gej_neg.y);
+    secp256k1_fe_normalize(&gej_neg.z);
+
+    multiset_from_gej_var(&r2, &gej_neg);
+
+    /* This is equivalent to a removal due to multisets being associative */
+    secp256k1_multiset_combine(ctx, &r1, &r2);
+    CHECK_EQUAL(&empty, &r1); /* M() == M(X)+M(-X) == M(X)-M(X) */
 }