diff --git a/backends/tpm/tpm_emulator.c b/backends/tpm/tpm_emulator.c
index 5a8fba9bde..b0e2fb3fc7 100644
--- a/backends/tpm/tpm_emulator.c
+++ b/backends/tpm/tpm_emulator.c
@@ -72,7 +72,7 @@ struct TPMEmulator {
     CharBackend ctrl_chr;
     QIOChannel *data_ioc;
     TPMVersion tpm_version;
-    ptm_cap caps; /* capabilities of the TPM */
+    uint32_t caps; /* capabilities of the TPM */
     uint8_t cur_locty_number; /* last set locality */
     Error *migration_blocker;
 
@@ -239,13 +239,15 @@ static void tpm_emulator_handle_request(TPMBackend *tb, TPMBackendCmd *cmd,
 
 static int tpm_emulator_probe_caps(TPMEmulator *tpm_emu)
 {
+    ptm_cap_n cap_n;
+
     if (tpm_emulator_ctrlcmd(tpm_emu, CMD_GET_CAPABILITY,
-                             &tpm_emu->caps, 0, sizeof(tpm_emu->caps)) < 0) {
+                             &cap_n, 0, sizeof(cap_n)) < 0) {
         error_report("tpm-emulator: probing failed : %s", strerror(errno));
         return -1;
     }
 
-    tpm_emu->caps = be64_to_cpu(tpm_emu->caps);
+    tpm_emu->caps = be32_to_cpu(cap_n.u.resp.caps);
 
     trace_tpm_emulator_probe_caps(tpm_emu->caps);
 
@@ -254,7 +256,7 @@ static int tpm_emulator_probe_caps(TPMEmulator *tpm_emu)
 
 static int tpm_emulator_check_caps(TPMEmulator *tpm_emu)
 {
-    ptm_cap caps = 0;
+    uint32_t caps = 0;
     const char *tpm = NULL;
 
     /* check for min. required capabilities */
@@ -527,8 +529,8 @@ static size_t tpm_emulator_get_buffer_size(TPMBackend *tb)
 static int tpm_emulator_block_migration(TPMEmulator *tpm_emu)
 {
     Error *err = NULL;
-    ptm_cap caps = PTM_CAP_GET_STATEBLOB | PTM_CAP_SET_STATEBLOB |
-                   PTM_CAP_STOP;
+    uint32_t caps = PTM_CAP_GET_STATEBLOB | PTM_CAP_SET_STATEBLOB |
+                    PTM_CAP_STOP;
 
     if (!TPM_EMULATOR_IMPLEMENTS_ALL_CAPS(tpm_emu, caps)) {
         error_setg(&tpm_emu->migration_blocker,
diff --git a/backends/tpm/tpm_ioctl.h b/backends/tpm/tpm_ioctl.h
index 1933ab6855..ee2dd15d35 100644
--- a/backends/tpm/tpm_ioctl.h
+++ b/backends/tpm/tpm_ioctl.h
@@ -29,6 +29,16 @@
 
 typedef uint32_t ptm_res;
 
+/* PTM_GET_CAPABILITY: Get supported capabilities (ioctl's) */
+struct ptm_cap_n {
+    union {
+        struct {
+            ptm_res tpm_result; /* will always be TPM_SUCCESS (0) */
+            uint32_t caps;
+        } resp; /* response */
+    } u;
+};
+
 /* PTM_GET_TPMESTABLISHED: get the establishment bit */
 struct ptm_est {
     union {
@@ -242,7 +252,8 @@ struct ptm_lockstorage {
     } u;
 };
 
-typedef uint64_t ptm_cap;
+typedef uint64_t ptm_cap; /* CUSE-only; use ptm_cap_n otherwise */
+typedef struct ptm_cap_n ptm_cap_n;
 typedef struct ptm_est ptm_est;
 typedef struct ptm_reset_est ptm_reset_est;
 typedef struct ptm_loc ptm_loc;
diff --git a/backends/tpm/trace-events b/backends/tpm/trace-events
index cb5cfa6510..05e30533ce 100644
--- a/backends/tpm/trace-events
+++ b/backends/tpm/trace-events
@@ -16,7 +16,7 @@ tpm_util_show_buffer_content(const char *buf) "%s"
 # tpm_emulator.c
 tpm_emulator_set_locality(uint8_t locty) "setting locality to %d"
 tpm_emulator_handle_request(void) "processing TPM command"
-tpm_emulator_probe_caps(uint64_t caps) "capabilities: 0x%"PRIx64
+tpm_emulator_probe_caps(uint32_t caps) "capabilities: 0x%x"
 tpm_emulator_set_buffer_size(uint32_t buffersize, uint32_t minsize, uint32_t maxsize) "buffer size: %u, min: %u, max: %u"
 tpm_emulator_startup_tpm_resume(bool is_resume, size_t buffersize) "is_resume: %d, buffer size: %zu"
 tpm_emulator_get_tpm_established_flag(uint8_t flag) "got established flag: %d"