diff --git a/msvc/libdivecomputer.vcproj b/msvc/libdivecomputer.vcproj
index c194f9f..242276a 100644
--- a/msvc/libdivecomputer.vcproj
+++ b/msvc/libdivecomputer.vcproj
@@ -692,6 +692,10 @@
 				RelativePath="..\include\libdivecomputer\parser.h"
 				>
 			</File>
+			<File
+				RelativePath="..\src\platform.h"
+				>
+			</File>
 			<File
 				RelativePath="..\src\rbstream.h"
 				>
diff --git a/src/Makefile.am b/src/Makefile.am
index 387b284..97062e1 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -63,6 +63,7 @@ libdivecomputer_la_SOURCES = \
 	diverite_nitekq.h diverite_nitekq.c diverite_nitekq_parser.c \
 	citizen_aqualand.h citizen_aqualand.c citizen_aqualand_parser.c \
 	divesystem_idive.h divesystem_idive.c divesystem_idive_parser.c \
+	platform.h \
 	ringbuffer.h ringbuffer.c \
 	rbstream.h rbstream.c \
 	checksum.h checksum.c \
diff --git a/src/hw_ostc3.c b/src/hw_ostc3.c
index a1a5efd..7ce7fd5 100644
--- a/src/hw_ostc3.c
+++ b/src/hw_ostc3.c
@@ -30,10 +30,7 @@
 #include "serial.h"
 #include "array.h"
 #include "aes.h"
-
-#ifdef _MSC_VER
-#define snprintf _snprintf
-#endif
+#include "platform.h"
 
 #define ISINSTANCE(device) dc_device_isinstance((device), &hw_ostc3_device_vtable)
 
diff --git a/src/irda.c b/src/irda.c
index 0f20970..d085ec0 100644
--- a/src/irda.c
+++ b/src/irda.c
@@ -53,6 +53,7 @@
 #include "common-private.h"
 #include "context-private.h"
 #include "array.h"
+#include "platform.h"
 
 #ifdef _WIN32
 typedef int s_ssize_t;
@@ -82,10 +83,6 @@ typedef int s_errcode_t;
 #define S_CLOSE close
 #endif
 
-#ifdef _MSC_VER
-#define snprintf _snprintf
-#endif
-
 struct dc_irda_t {
 	dc_context_t *context;
 #ifdef _WIN32
diff --git a/src/platform.h b/src/platform.h
new file mode 100644
index 0000000..877e320
--- /dev/null
+++ b/src/platform.h
@@ -0,0 +1,50 @@
+/*
+ * libdivecomputer
+ *
+ * Copyright (C) 2017 Jef Driesen
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301 USA
+ */
+
+#ifndef DC_PLATFORM_H
+#define DC_PLATFORM_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif /* __cplusplus */
+
+#ifdef _WIN32
+#define DC_PRINTF_SIZE "%Iu"
+#else
+#define DC_PRINTF_SIZE "%zu"
+#endif
+
+#ifdef _MSC_VER
+#define snprintf _snprintf
+#define strcasecmp _stricmp
+#if _MSC_VER < 1800
+// The rint() function is only available in MSVC 2013 and later
+// versions. Our replacement macro isn't entirely correct, because the
+// rounding rules for halfway cases are slightly different (away from
+// zero vs to even). But for our use-case, that's not a problem.
+#define rint(x) ((x) >= 0.0 ? floor((x) + 0.5): ceil((x) - 0.5))
+#endif
+#endif
+
+#ifdef __cplusplus
+}
+#endif /* __cplusplus */
+#endif /* DC_PLATFORM_H */
diff --git a/src/suunto_eonsteel.c b/src/suunto_eonsteel.c
index 2e6d4c4..07cd85c 100644
--- a/src/suunto_eonsteel.c
+++ b/src/suunto_eonsteel.c
@@ -28,10 +28,7 @@
 #include "device-private.h"
 #include "array.h"
 #include "usbhid.h"
-
-#ifdef _MSC_VER
-#define snprintf _snprintf
-#endif
+#include "platform.h"
 
 typedef struct suunto_eonsteel_device_t {
 	dc_device_t base;
@@ -140,7 +137,7 @@ static int receive_packet(suunto_eonsteel_device_t *eon, unsigned char *buffer,
 		return -1;
 	}
 	if (transferred != PACKET_SIZE) {
-		ERROR(eon->base.context, "incomplete read interrupt transfer (got %zu, expected %d)", transferred, PACKET_SIZE);
+		ERROR(eon->base.context, "incomplete read interrupt transfer (got " DC_PRINTF_SIZE ", expected %d)", transferred, PACKET_SIZE);
 		return -1;
 	}
 	if (buf[0] != 0x3f) {
diff --git a/src/suunto_eonsteel_parser.c b/src/suunto_eonsteel_parser.c
index 0ebee01..a7f817d 100644
--- a/src/suunto_eonsteel_parser.c
+++ b/src/suunto_eonsteel_parser.c
@@ -28,17 +28,7 @@
 #include "context-private.h"
 #include "parser-private.h"
 #include "array.h"
-
-#ifdef _MSC_VER
-#define strcasecmp _stricmp
-#if _MSC_VER < 1800
-// The rint() function is only available in MSVC 2013 and later
-// versions. Our replacement macro isn't entirely correct, because the
-// rounding rules for halfway cases are slightly different (away from
-// zero vs to even). But for our use-case, that's not a problem.
-#define rint(x) ((x) >= 0.0 ? floor((x) + 0.5): ceil((x) - 0.5))
-#endif
-#endif
+#include "platform.h"
 
 #define C_ARRAY_SIZE(a) (sizeof(a) / sizeof(*(a)))
 
diff --git a/src/uwatec_g2.c b/src/uwatec_g2.c
index 6e35104..f6b0b02 100644
--- a/src/uwatec_g2.c
+++ b/src/uwatec_g2.c
@@ -28,6 +28,7 @@
 #include "device-private.h"
 #include "usbhid.h"
 #include "array.h"
+#include "platform.h"
 
 #define ISINSTANCE(device) dc_device_isinstance((device), &uwatec_g2_device_vtable)
 
@@ -76,7 +77,7 @@ receive_data (uwatec_g2_device_t *device, dc_event_progress_t *progress, unsigne
 			return rc;
 		}
 		if (transferred != PACKET_SIZE) {
-			ERROR (device->base.context, "incomplete read interrupt transfer (got %zu, expected %d)", transferred, PACKET_SIZE);
+			ERROR (device->base.context, "incomplete read interrupt transfer (got " DC_PRINTF_SIZE  ", expected %d)", transferred, PACKET_SIZE);
 			return DC_STATUS_PROTOCOL;
 		}
 		len = buf[0];