diff --git a/src/content/ContentLoader.cpp b/src/content/ContentLoader.cpp
index 5fe39b1b..8daf1dcb 100644
--- a/src/content/ContentLoader.cpp
+++ b/src/content/ContentLoader.cpp
@@ -241,17 +241,22 @@ void ContentLoader::loadBlock(
     // block light emission [r, g, b] where r,g,b in range [0..15]
     if (auto found = root.at("emission")) {
         const auto& emissionarr = *found;
-        def.emission[0] = emissionarr[0].asNumber();
-        def.emission[1] = emissionarr[1].asNumber();
-        def.emission[2] = emissionarr[2].asNumber();
+        def.emission[0] = emissionarr[0].asInteger();
+        def.emission[1] = emissionarr[1].asInteger();
+        def.emission[2] = emissionarr[2].asInteger();
     }
 
     // block size
     if (auto found = root.at("size")) {
         const auto& sizearr = *found;
-        def.size.x = sizearr[0].asNumber();
-        def.size.y = sizearr[1].asNumber();
-        def.size.z = sizearr[2].asNumber();
+        def.size.x = sizearr[0].asInteger();
+        def.size.y = sizearr[1].asInteger();
+        def.size.z = sizearr[2].asInteger();
+        if (def.size.x < 1 || def.size.y < 1 || def.size.z < 1) {
+            throw std::runtime_error(
+                "block " + util::quote(def.name) + ": invalid block size"
+            );
+        }
         if (def.model == BlockModel::block &&
             (def.size.x != 1 || def.size.y != 1 || def.size.z != 1)) {
             def.model = BlockModel::aabb;