diff --git a/src/ifcparse/IfcParse.h b/src/ifcparse/IfcParse.h
index 8b0edf4880..484345128f 100644
--- a/src/ifcparse/IfcParse.h
+++ b/src/ifcparse/IfcParse.h
@@ -55,18 +55,6 @@
 
 #include "../ifcparse/IfcSpfStream.h"
 
-#if defined(__clang__)
-# define my_thread_local thread_local
-#elif defined(__GNUC__)
-# define my_thread_local __thread
-#elif __STDC_VERSION__ >= 201112L
-# define my_thread_local _Thread_local
-#elif defined(_MSC_VER)
-# define my_thread_local __declspec(thread)
-#else
-# error Cannot define thread_local
-#endif
-
 namespace IfcParse {
 
 	class IfcFile;
diff --git a/src/ifcparse/IfcSchema.cpp b/src/ifcparse/IfcSchema.cpp
index 9f4fcf6c02..6c7bee5b0c 100644
--- a/src/ifcparse/IfcSchema.cpp
+++ b/src/ifcparse/IfcSchema.cpp
@@ -4,7 +4,14 @@
 #include <map>
 
 bool IfcParse::declaration::is(const std::string& name) const {
-	if (name_lower_ == boost::to_lower_copy(name)) return true;
+	const std::string* name_ptr = &name;
+	if (std::any_of(name.begin(), name.end(), [](char c) { return std::islower(c); })) {
+		temp_string_() = name;
+		boost::to_upper(temp_string_());
+		name_ptr = &temp_string_();
+	}
+
+	if (name_upper_ == *name_ptr) return true;
 
 	if (this->as_entity()) {
 		return this->as_entity()->is(name);
diff --git a/src/ifcparse/IfcSchema.h b/src/ifcparse/IfcSchema.h
index b11a115982..cb5abca5ca 100644
--- a/src/ifcparse/IfcSchema.h
+++ b/src/ifcparse/IfcSchema.h
@@ -24,6 +24,7 @@
 #include <vector>
 #include <algorithm>
 #include <iterator>
+#include <cctype>
 
 #include <boost/algorithm/string.hpp>
 
@@ -123,14 +124,19 @@ namespace IfcParse {
 		friend class schema_definition;
 
 	protected:
-		std::string name_, name_lower_;
+		std::string name_, name_upper_;
 		int index_in_schema_;
 		mutable const schema_definition* schema_;
 
+		std::string& temp_string_() const {
+			static my_thread_local std::string s;
+			return s;
+		}
+
 	public:
 		declaration(const std::string& name, int index_in_schema)
 			: name_(name)
-			, name_lower_(boost::to_lower_copy(name))
+			, name_upper_(boost::to_upper_copy(name))
 			, index_in_schema_(index_in_schema)
 			, schema_(0)
 		{}
@@ -138,7 +144,7 @@ namespace IfcParse {
 		virtual ~declaration() {}
 
 		const std::string& name() const { return name_; }
-		const std::string& name_lc() const { return name_lower_; }
+		const std::string& name_uc() const { return name_upper_; }
 
 		virtual const type_declaration* as_type_declaration() const { return static_cast<type_declaration*>(0); }
 		virtual const select_type* as_select_type() const { return static_cast<select_type*>(0); }
@@ -416,7 +422,7 @@ namespace IfcParse {
 		class declaration_by_name_cmp {
 		public:
 			bool operator()(const declaration* decl, const std::string& name) {
-				return decl->name_lc() < name;
+				return decl->name_uc() < name;
 			}
 		};
 
@@ -429,6 +435,11 @@ namespace IfcParse {
 
 		instance_factory* factory_;
 
+		std::string& temp_string_() const {
+			static my_thread_local std::string s;
+			return s;
+		}
+
 	public:
 
 		schema_definition(const std::string& name, const std::vector<const declaration*>& declarations, instance_factory* factory);
@@ -436,9 +447,14 @@ namespace IfcParse {
 		~schema_definition();
 
 		const declaration* declaration_by_name(const std::string& name) const {
-			const std::string name_lower = boost::to_lower_copy(name);
-			std::vector<const declaration*>::const_iterator it = std::lower_bound(declarations_.begin(), declarations_.end(), name_lower, declaration_by_name_cmp());
-			if (it == declarations_.end() || (**it).name_lc() != name_lower) {
+			const std::string* name_ptr = &name;
+			if (std::any_of(name.begin(), name.end(), [](char c) { return std::islower(c); })) {
+				temp_string_() = name;
+				boost::to_upper(temp_string_());
+				name_ptr = &temp_string_();
+			}
+			std::vector<const declaration*>::const_iterator it = std::lower_bound(declarations_.begin(), declarations_.end(), *name_ptr, declaration_by_name_cmp());
+			if (it == declarations_.end() || (**it).name_uc() != *name_ptr) {
 				throw IfcParse::IfcException("Entity with '" + name + "' not found");
 			} else {
 				return *it;
diff --git a/src/ifcparse/ifc_parse_api.h b/src/ifcparse/ifc_parse_api.h
index b2dec0ba1d..6a92c6d152 100644
--- a/src/ifcparse/ifc_parse_api.h
+++ b/src/ifcparse/ifc_parse_api.h
@@ -34,4 +34,17 @@
   #define IFC_PARSE_API
 #endif
 
+#if defined(__clang__)
+# define my_thread_local thread_local
+#elif defined(__GNUC__)
+# define my_thread_local __thread
+#elif __STDC_VERSION__ >= 201112L
+# define my_thread_local _Thread_local
+#elif defined(_MSC_VER)
+# define my_thread_local __declspec(thread)
+#elif defined(SWIG)
+#else
+# error Cannot define thread_local
+#endif
+
 #endif