diff --git a/Makefile b/Makefile
index b12029e..0c075e0 100644
--- a/Makefile
+++ b/Makefile
@@ -142,7 +142,7 @@
 	-Wundef -Wmissing-prototypes -Wno-trigraphs -Wredundant-decls -Wshadow \
 	-Wwrite-strings -Wstrict-aliasing -Wdate-time -Wno-unknown-warning \
 	-Wno-address-of-packed-member -ffunction-sections -fdata-sections \
-	-Wimplicit-fallthrough ${DEBUG_FLAGS}
+	-Wimplicit-fallthrough -Wformat -Wno-format-security ${DEBUG_FLAGS}
 
 # Note: FIRMWARE_ARCH is defined by the Chromium OS ebuild.
 ifeq (${FIRMWARE_ARCH},arm)
diff --git a/firmware/2lib/include/2api.h b/firmware/2lib/include/2api.h
index 52e5a4a..e8ce89d 100644
--- a/firmware/2lib/include/2api.h
+++ b/firmware/2lib/include/2api.h
@@ -804,6 +804,7 @@
  * @param func		Function name generating output, or NULL.
  * @param fmt		Printf format string
  */
+__attribute__((format(printf, 2, 3)))
 void vb2ex_printf(const char *func, const char *fmt, ...);
 
 /**
diff --git a/futility/cmd_sign.c b/futility/cmd_sign.c
index 109287c..c69f712 100644
--- a/futility/cmd_sign.c
+++ b/futility/cmd_sign.c
@@ -223,7 +223,7 @@
 		fprintf(stderr, "Unable to sign kernel blob\n");
 		return 1;
 	}
-	VB2_DEBUG("vblock_size = 0x%" PRIx64 "\n", vblock_size);
+	VB2_DEBUG("vblock_size = %#x\n", vblock_size);
 
 	if (sign_option.create_new_outfile) {
 		/* Write out what we've been asked for */
diff --git a/futility/file_type_bios.c b/futility/file_type_bios.c
index 9d45269..7e805f5 100644
--- a/futility/file_type_bios.c
+++ b/futility/file_type_bios.c
@@ -467,7 +467,7 @@
 			state.area[c].buf = buf + ah->area_offset;
 			state.area[c].len = ah->area_size;
 
-			VB2_DEBUG("%s() examining FMAP area %d (%s),"
+			VB2_DEBUG("examining FMAP area %d (%s),"
 				  " offset=0x%08x len=0x%08x\n",
 				  c, ah_name, ah->area_offset, ah->area_size);
 
diff --git a/futility/file_type_rwsig.c b/futility/file_type_rwsig.c
index c5616e5..bcccb2d 100644
--- a/futility/file_type_rwsig.c
+++ b/futility/file_type_rwsig.c
@@ -112,7 +112,7 @@
 
 		sig_size = fmaparea->area_size;
 
-		VB2_DEBUG("Looking for signature at %#x (%#x)\n",
+		VB2_DEBUG("Looking for signature at %#tx (%#x)\n",
 			  (uint8_t*)sig - buf, sig_size);
 
 		if (VB2_SUCCESS != vb21_verify_signature(sig, sig_size))
@@ -235,7 +235,7 @@
 
 			sig_size = fmaparea->area_size;
 
-			VB2_DEBUG("Looking for signature at %#x (%#x)\n",
+			VB2_DEBUG("Looking for signature at %#tx (%#x)\n",
 				  (uint8_t*)old_sig - buf, sig_size);
 
 			data = fmap_find_by_name(buf, len, fmap, "EC_RW",
diff --git a/futility/file_type_usbpd1.c b/futility/file_type_usbpd1.c
index 8065041..42cb62c 100644
--- a/futility/file_type_usbpd1.c
+++ b/futility/file_type_usbpd1.c
@@ -95,7 +95,7 @@
 	uint32_t rw_offset;
 	uint32_t r;
 
-	VB2_DEBUG("%s(): name %s len  0x%08x (%d)\n", name, len, len);
+	VB2_DEBUG("name %s len  %#.8x (%d)\n", name, len, len);
 
 	/* Get image locations */
 	if (!parse_size_opts(len, &ro_size, &rw_size, &ro_offset, &rw_offset))
diff --git a/futility/vb1_helper.c b/futility/vb1_helper.c
index 7439182..cdc3925 100644
--- a/futility/vb1_helper.c
+++ b/futility/vb1_helper.c
@@ -185,8 +185,8 @@
 		}
 		kernel32_size = kernel_size - kernel32_start;
 
-		VB2_DEBUG(" kernel16_start=0x%" PRIx64 "\n", 0);
-		VB2_DEBUG(" kernel16_size=0x%" PRIx64 "\n", kernel32_start);
+		VB2_DEBUG(" kernel16_start=%#x\n", 0);
+		VB2_DEBUG(" kernel16_size=%#x\n", kernel32_start);
 
 		/* Copy the original zeropage data from kernel_buf into
 		 * g_param_data, then tweak a few fields for our purposes */
@@ -221,8 +221,8 @@
 		break;
 	}
 
-	VB2_DEBUG(" kernel32_start=0x%" PRIx64 "\n", kernel32_start);
-	VB2_DEBUG(" kernel32_size=0x%" PRIx64 "\n", kernel32_size);
+	VB2_DEBUG(" kernel32_start=%#x\n", kernel32_start);
+	VB2_DEBUG(" kernel32_size=%#x\n", kernel32_size);
 
 	/* Keep just the 32-bit kernel. */
 	if (kernel32_size) {
@@ -461,7 +461,7 @@
 	FILE *f;
 
 	/* Write the output file */
-	VB2_DEBUG("writing %s with 0x%" PRIx64 ", 0x%" PRIx64 "\n",
+	VB2_DEBUG("writing %s with %#x, %#x\n",
 		  outfile, part1_size, part2_size);
 
 	f = fopen(outfile, "wb");
@@ -674,7 +674,7 @@
 	 * devices.
 	 */
 	g_kernel_blob_size = roundup(g_kernel_blob_size, CROS_ALIGN);
-	VB2_DEBUG("g_kernel_blob_size  0x%" PRIx64 "\n", g_kernel_blob_size);
+	VB2_DEBUG("g_kernel_blob_size  %#x\n", g_kernel_blob_size);
 
 	/* Allocate space for the blob. */
 	g_kernel_blob_data = malloc(g_kernel_blob_size);
@@ -682,22 +682,22 @@
 
 	/* Assign the sub-pointers */
 	g_kernel_data = g_kernel_blob_data + now;
-	VB2_DEBUG("g_kernel_size       0x%" PRIx64 " ofs 0x%" PRIx64 "\n",
+	VB2_DEBUG("g_kernel_size       %#x ofs %#x\n",
 		  g_kernel_size, now);
 	now += roundup(g_kernel_size, CROS_ALIGN);
 
 	g_config_data = g_kernel_blob_data + now;
-	VB2_DEBUG("g_config_size       0x%" PRIx64 " ofs 0x%" PRIx64 "\n",
+	VB2_DEBUG("g_config_size       %#x ofs %#x\n",
 		  g_config_size, now);
 	now += g_config_size;
 
 	g_param_data = g_kernel_blob_data + now;
-	VB2_DEBUG("g_param_size        0x%" PRIx64 " ofs 0x%" PRIx64 "\n",
+	VB2_DEBUG("g_param_size        %#x ofs %#x\n",
 		  g_param_size, now);
 	now += g_param_size;
 
 	g_bootloader_data = g_kernel_blob_data + now;
-	VB2_DEBUG("g_bootloader_size   0x%" PRIx64 " ofs 0x%" PRIx64 "\n",
+	VB2_DEBUG("g_bootloader_size   %#x ofs %#x\n",
 		  g_bootloader_size, now);
 	g_ondisk_bootloader_addr = kernel_body_load_address + now;
 	VB2_DEBUG("g_ondisk_bootloader_addr   0x%" PRIx64 "\n",
@@ -706,14 +706,14 @@
 
 	if (g_vmlinuz_header_size) {
 		g_vmlinuz_header_data = g_kernel_blob_data + now;
-		VB2_DEBUG("g_vmlinuz_header_size 0x%" PRIx64 " ofs 0x%" PRIx64 "\n",
+		VB2_DEBUG("g_vmlinuz_header_size %#x ofs %#x\n",
 			  g_vmlinuz_header_size, now);
 		g_ondisk_vmlinuz_header_addr = kernel_body_load_address + now;
 		VB2_DEBUG("g_ondisk_vmlinuz_header_addr   0x%" PRIx64 "\n",
 			  g_ondisk_vmlinuz_header_addr);
 	}
 
-	VB2_DEBUG("end of kern_blob at kern_blob+0x%" PRIx64 "\n", now);
+	VB2_DEBUG("end of kern_blob at kern_blob+%#x\n", now);
 
 	/* Copy the kernel and params bits into the correct places */
 	if (0 != PickApartVmlinuz(vmlinuz_buf, vmlinuz_size,