diff --git a/parseinstrs.py b/parseinstrs.py
index a62f3b3..104c021 100644
--- a/parseinstrs.py
+++ b/parseinstrs.py
@@ -142,7 +142,7 @@ class InstrDesc(NamedTuple):
     def optype_str(self):
         optypes = ["", "", "", ""]
         flags = ENCODINGS[self.encoding]
-        if flags.modrm_idx:   optypes[flags.modrm_idx^3] = "M"
+        if flags.modrm_idx:   optypes[flags.modrm_idx^3] = "rM"[flags.modrm]
         if flags.modreg_idx:  optypes[flags.modreg_idx^3] = "r"
         if flags.vexreg_idx:  optypes[flags.vexreg_idx^3] = "r"
         if flags.zeroreg_idx: optypes[flags.zeroreg_idx^3] = "r"
diff --git a/tests/test_encode.c b/tests/test_encode.c
index d823501..0d0ce4d 100644
--- a/tests/test_encode.c
+++ b/tests/test_encode.c
@@ -82,6 +82,8 @@ main(int argc, char** argv)
     TEST("\x66\x0f\xa0", FE_PUSH16r, FE_FS);
     TEST("\x0f\xa8", FE_PUSHr, FE_GS);
     TEST("\x66\x0f\xa8", FE_PUSH16r, FE_GS);
+    TEST("\xff\x30", FE_PUSHm, FE_MEM(FE_AX, 0, 0, 0));
+    TEST("\xff\x31", FE_PUSHm, FE_MEM(FE_CX, 0, 0, 0));
     TEST("\x9c", FE_PUSHF);
     TEST("\xd2\xe4", FE_SHL8rr, FE_AH, FE_CX);
     TEST("", FE_SHL8rr, FE_AH, FE_DX);
@@ -90,7 +92,6 @@ main(int argc, char** argv)
     TEST("\xc1\xe0\x02", FE_SHL32ri, FE_AX, 2);
     TEST("\x48\xc1\xe0\x02", FE_SHL64ri, FE_AX, 2);
     TEST("\x48\xf7\x28", FE_IMUL64m, FE_MEM(FE_AX, 0, 0, 0));
-    // TEST("\x66\x90", FE_XCHG16rr, FE_AX, FE_AX);
     TEST("\xc2\x00\x00", FE_RETi, 0);
     TEST("\xff\xd0", FE_CALLr, FE_AX);
     TEST("\x05\x00\x01\x00\x00", FE_ADD32ri, FE_AX, 0x100);
@@ -134,6 +135,8 @@ main(int argc, char** argv)
     TEST("\x66\x90", FE_XCHG16rr, FE_AX, FE_AX);
     TEST("\x87\xc0", FE_XCHG32rr, FE_AX, FE_AX);
     TEST("\x48\x90", FE_XCHG64rr, FE_AX, FE_AX);
+    TEST("\x87\x00", FE_XCHG32mr, FE_MEM(FE_AX, 0, 0, 0), FE_AX);
+    TEST("\x87\x08", FE_XCHG32mr, FE_MEM(FE_AX, 0, 0, 0), FE_CX);
     TEST("\x90", FE_NOP);
     TEST("\x0f\x1f\xc0", FE_NOP32r, FE_AX);
     TEST("\x26\x01\x00", FE_ADD32mr|FE_SEG(FE_ES), FE_MEM(FE_AX, 0, 0, 0), FE_AX);