diff --git a/src/easymesh/easymesh.cpp b/src/easymesh/easymesh.cpp
index a3441c35..9d778fda 100644
--- a/src/easymesh/easymesh.cpp
+++ b/src/easymesh/easymesh.cpp
@@ -208,7 +208,8 @@ void GpuEasyMeshData::AddGpuData(GpuShaderData* gpudata, EasyMesh* src_mesh)
     BUILD_VFLAG(has_color,       VertexUsage::Color,        vflags);
     BUILD_VFLAG(has_texcoord,    VertexUsage::TexCoord,     vflags);
     BUILD_VFLAG_OR(has_texcoord, VertexUsage::TexCoordExt,  vflags);
-    ASSERT(!vflags, String("Vertex Useage setup is not implemented for : ") + VertexUsage::GetNameList(vflags) + String(", feel free to do so."));
+    ASSERT(!vflags, "Vertex Usage setup is not implemented for %s, feel free to do so.",
+           VertexUsage::GetNameList(vflags).C());
 
     if (has_position)   gpudata->AddAttribute(gpudata->GetInVertexName(),   VertexUsage::Position, 0);
     if (has_normal)     gpudata->AddAttribute(gpudata->GetInNormalName(),   VertexUsage::Normal, 0);
@@ -270,7 +271,8 @@ void GpuEasyMeshData::SetupVertexData(uint16_t vflags, EasyMesh* src_mesh)
     BUILD_VFLAG_COUNT(has_color,      VertexUsage::Color,       saveflags, flagnb);
     BUILD_VFLAG_COUNT(has_texcoord,   VertexUsage::TexCoord,    saveflags, flagnb);
     BUILD_VFLAG_COUNT(has_texcoordExt,VertexUsage::TexCoordExt, saveflags, flagnb);
-    ASSERT(!saveflags, String("Vertex Declaration setup is not implemented for : ") + VertexUsage::GetNameList(vflags) + String(", feel free to do so."));
+    ASSERT(!vflags, "Vertex Declaration setup is not implemented for %s, feel free to do so.",
+           VertexUsage::GetNameList(vflags).C());
 
     if (has_position && has_normal && has_color && has_texcoord && has_texcoordExt && flagnb == 5)
     {
@@ -396,7 +398,8 @@ void GpuEasyMeshData::RenderMeshData(mat4 const &model)
     BUILD_VFLAG(has_color,      VertexUsage::Color,       vflags);
     BUILD_VFLAG(has_texcoord,   VertexUsage::TexCoord,    vflags);
     BUILD_VFLAG_OR(has_texcoord,VertexUsage::TexCoordExt, vflags);
-    ASSERT(!vflags, String("Vertex Stream setup is not implemented for : ") + VertexUsage::GetNameList(vflags) + String(", feel free to do so."));
+    ASSERT(!vflags, "Vertex Streamsetup is not implemented for %s, feel free to do so.",
+           VertexUsage::GetNameList(vflags).C());
 
     int idx = 0;
     ShaderAttrib Attribs[4] = { lol::ShaderAttrib(), lol::ShaderAttrib(), lol::ShaderAttrib(), lol::ShaderAttrib() };