diff --git a/src/config.c b/src/config.c
index 13d0e8631a..313403297e 100644
--- a/src/config.c
+++ b/src/config.c
@@ -814,7 +814,7 @@ static void config_read_properties(config_section_definition **currentSection, c
 	} else {
 		if (*currentSection != NULL) {
 			utf8 *propertyName, *value;
-			int propertyNameSize, valueSize;
+			int propertyNameSize = 0, valueSize;
 			if (config_get_property_name_value(ch, &propertyName, &propertyNameSize, &value, &valueSize)) {
 				config_property_definition *property;
 				property = config_get_property_def(*currentSection, propertyName, propertyNameSize);
diff --git a/src/localisation/localisation.c b/src/localisation/localisation.c
index c89308c605..d383892707 100644
--- a/src/localisation/localisation.c
+++ b/src/localisation/localisation.c
@@ -672,7 +672,7 @@ static void format_comma_separated_fixed_1dp(char **dest, size_t *size, long lon
 	char tmp;
 	const char *commaMark = language_get_string(STR_LOCALE_THOUSANDS_SEPARATOR);
 	const char *decimalMark = language_get_string(STR_LOCALE_DECIMAL_POINT);
-	const char *ch;
+	const char *ch = NULL;
 	int zeroNeeded = 1;
 	
 	if ((*size) == 0) return;
diff --git a/src/network/http.cpp b/src/network/http.cpp
index dbb589a6af..09dc0f91f5 100644
--- a/src/network/http.cpp
+++ b/src/network/http.cpp
@@ -118,7 +118,7 @@ http_json_response *http_request_json(const http_json_request *request)
 	CURL *curl;
 	CURLcode curlResult;
 	http_json_response *response;
-	read_buffer readBuffer;
+	read_buffer readBuffer = { 0 };
 	write_buffer writeBuffer;
 
 	curl = curl_easy_init();
diff --git a/src/paint/map_element/surface.c b/src/paint/map_element/surface.c
index 1ef953a3c4..e45e672984 100644
--- a/src/paint/map_element/surface.c
+++ b/src/paint/map_element/surface.c
@@ -336,9 +336,9 @@ static void viewport_surface_smoothen_edge(enum edge edge, struct tile_descripto
 		return;
 	}
 
-	uint32 maskImageBase;
-	uint8 neighbourCorners[2];
-	uint8 ownCorners[2];
+	uint32 maskImageBase = 0;
+	uint8 neighbourCorners[2] = { 0 };
+	uint8 ownCorners[2] = { 0 };
 
 	switch (edge) {
 		case EDGE_BOTTOMLEFT:
@@ -376,7 +376,7 @@ static void viewport_surface_smoothen_edge(enum edge edge, struct tile_descripto
 		return;
 	}
 
-	uint8 dh, cl;
+	uint8 dh = 0, cl = 0;
 	switch(edge) {
 		case EDGE_BOTTOMLEFT:
 			dh = byte_97B524[byte_97B444[self.slope]];
diff --git a/src/util/sawyercoding.c b/src/util/sawyercoding.c
index ddb180e85a..4db38ba8c9 100644
--- a/src/util/sawyercoding.c
+++ b/src/util/sawyercoding.c
@@ -465,7 +465,7 @@ static size_t encode_chunk_repeat(const uint8 *src_buffer, uint8 *dst_buffer, si
 {
 	size_t i, j, outLength;
 	size_t searchIndex, searchEnd, maxRepeatCount;
-	size_t bestRepeatIndex, bestRepeatCount, repeatIndex, repeatCount;
+	size_t bestRepeatIndex = 0, bestRepeatCount = 0, repeatIndex, repeatCount;
 
 	if (length == 0)
 		return 0;
diff --git a/src/windows/text_input.c b/src/windows/text_input.c
index 2e45c53d78..7280eb8b4d 100644
--- a/src/windows/text_input.c
+++ b/src/windows/text_input.c
@@ -278,7 +278,7 @@ static void window_text_input_paint(rct_window *w, rct_drawpixelinfo *dpi)
 	size_t char_count = 0;
 	uint8 cur_drawn = 0;
 
-	int cursorX, cursorY;
+	int cursorX = 0, cursorY = 0;
 	for (int line = 0; line <= no_lines; line++) {
 		gfx_draw_string(dpi, wrap_pointer, w->colours[1], w->x + 12, y);