diff --git a/include/attribute_store.h b/include/attribute_store.h
index dc210b96..498c6c6c 100644
--- a/include/attribute_store.h
+++ b/include/attribute_store.h
@@ -42,13 +42,13 @@ class AttributeKeyStore {
 	std::map<const std::string*, uint16_t, string_ptr_less_than> keys2index;
 };
 
-enum class AttributePairType: char { Bool = 0, Float = 1, String = 2 };
+enum class AttributePairType: uint8_t { Bool = 0, Float = 1, String = 2 };
 // AttributePair is a key/value pair (with minzoom)
 #pragma pack(push, 1)
 struct AttributePair {
 	short keyIndex : 9;
-	AttributePairType valueType : 3;
-	char minzoom : 4;
+	AttributePairType valueType : 2;
+	uint8_t minzoom : 5; // Support zooms from 0..31. In practice, we expect z16 to be the biggest minzoom.
 	union {
 		float floatValue_;
 		PooledString stringValue_;
diff --git a/test/attribute_store.test.cpp b/test/attribute_store.test.cpp
index db104a14..aa721787 100644
--- a/test/attribute_store.test.cpp
+++ b/test/attribute_store.test.cpp
@@ -11,10 +11,10 @@ MU_TEST(test_attribute_store) {
 
 	AttributeSet s1;
 	store.addAttribute(s1, "str1", std::string("someval"), 0);
-	store.addAttribute(s1, "str2", std::string("a very long string"), 0);
+	store.addAttribute(s1, "str2", std::string("a very long string"), 14);
 	store.addAttribute(s1, "bool1", false, 0);
 	store.addAttribute(s1, "bool2", true, 0);
-	store.addAttribute(s1, "float1", (float)42.0, 0);
+	store.addAttribute(s1, "float1", (float)42.0, 4);
 
 	const auto s1Index = store.add(s1);
 
@@ -35,6 +35,7 @@ MU_TEST(test_attribute_store) {
 	mu_check(str2 != s1Pairs.end());
 	mu_check((*str2)->hasStringValue());
 	mu_check((*str2)->stringValue() == "a very long string");
+	mu_check((*str2)->minzoom == 14);
 
 	const auto bool1 = std::find_if(s1Pairs.begin(), s1Pairs.end(), [&store](auto ap) {
 			return ap->keyIndex == store.keyStore.key2index("bool1");
@@ -56,6 +57,7 @@ MU_TEST(test_attribute_store) {
 	mu_check(float1 != s1Pairs.end());
 	mu_check((*float1)->hasFloatValue());
 	mu_check((*float1)->floatValue() == 42);
+	mu_check((*float1)->minzoom == 4);
 }
 
 MU_TEST(test_attribute_store_reuses) {