diff --git a/target/s390x/mem_helper.c b/target/s390x/mem_helper.c
index e21a47fb4d..c94dbf3fcb 100644
--- a/target/s390x/mem_helper.c
+++ b/target/s390x/mem_helper.c
@@ -1442,7 +1442,7 @@ static uint32_t do_csst(CPUS390XState *env, uint32_t r3, uint64_t a1,
     }
 
     /* Sanity check the alignments.  */
-    if (extract32(a1, 0, 4 << fc) || extract32(a2, 0, 1 << sc)) {
+    if (extract32(a1, 0, fc + 2) || extract32(a2, 0, sc)) {
         goto spec_exception;
     }
 
diff --git a/target/s390x/translate.c b/target/s390x/translate.c
index 9caae5af84..4f62a38c97 100644
--- a/target/s390x/translate.c
+++ b/target/s390x/translate.c
@@ -2058,9 +2058,9 @@ static DisasJumpType op_csst(DisasContext *s, DisasOps *o)
     TCGv_i32 t_r3 = tcg_const_i32(r3);
 
     if (tb_cflags(s->base.tb) & CF_PARALLEL) {
-        gen_helper_csst_parallel(cc_op, cpu_env, t_r3, o->in1, o->in2);
+        gen_helper_csst_parallel(cc_op, cpu_env, t_r3, o->addr1, o->in2);
     } else {
-        gen_helper_csst(cc_op, cpu_env, t_r3, o->in1, o->in2);
+        gen_helper_csst(cc_op, cpu_env, t_r3, o->addr1, o->in2);
     }
     tcg_temp_free_i32(t_r3);
 
diff --git a/tests/tcg/s390x/Makefile.target b/tests/tcg/s390x/Makefile.target
index 9f4076901f..f62f950d8e 100644
--- a/tests/tcg/s390x/Makefile.target
+++ b/tests/tcg/s390x/Makefile.target
@@ -1,3 +1,4 @@
 VPATH+=$(SRC_PATH)/tests/tcg/s390x
 CFLAGS+=-march=zEC12 -m64
 TESTS+=hello-s390x
+TESTS+=csst
diff --git a/tests/tcg/s390x/csst.c b/tests/tcg/s390x/csst.c
new file mode 100644
index 0000000000..1dae9071fb
--- /dev/null
+++ b/tests/tcg/s390x/csst.c
@@ -0,0 +1,43 @@
+#include <stdint.h>
+#include <unistd.h>
+
+int main(void)
+{
+    uint64_t parmlist[] = {
+        0xfedcba9876543210ull,
+        0,
+        0x7777777777777777ull,
+        0,
+    };
+    uint64_t op1 = 0x0123456789abcdefull;
+    uint64_t op2 = 0;
+    uint64_t op3 = op1;
+    uint64_t cc;
+
+    asm volatile(
+        "    lghi %%r0,%[flags]\n"
+        "    la %%r1,%[parmlist]\n"
+        "    csst %[op1],%[op2],%[op3]\n"
+        "    ipm %[cc]\n"
+        : [op1] "+m" (op1),
+          [op2] "+m" (op2),
+          [op3] "+r" (op3),
+          [cc] "=r" (cc)
+        : [flags] "K" (0x0301),
+          [parmlist] "m" (parmlist)
+        : "r0", "r1", "cc", "memory");
+    cc = (cc >> 28) & 3;
+    if (cc) {
+        write(1, "bad cc\n", 7);
+        return 1;
+    }
+    if (op1 != parmlist[0]) {
+        write(1, "bad op1\n", 8);
+        return 1;
+    }
+    if (op2 != parmlist[2]) {
+        write(1, "bad op2\n", 8);
+        return 1;
+    }
+    return 0;
+}