diff --git a/STM32Make.make b/STM32Make.make
index 98b3b4a..8bee06a 100644
--- a/STM32Make.make
+++ b/STM32Make.make
@@ -565,8 +565,14 @@ vpath %.cpp $(sort $(dir $(CPP_SOURCES)))
 # list of C objects
 OBJECTS += $(addprefix $(BUILD_DIR)/,$(notdir $(C_SOURCES:.c=.o)))
 vpath %.c $(sort $(dir $(C_SOURCES)))
+
 # list of ASM program objects
-OBJECTS += $(addprefix $(BUILD_DIR)/,$(notdir $(ASM_SOURCES:.s=.o)))
+# list of ASM program objects
+UPPER_CASE_ASM_SOURCES = $(filter %.S,$(ASM_SOURCES))
+LOWER_CASE_ASM_SOURCES = $(filter %.s,$(ASM_SOURCES))
+
+OBJECTS += $(addprefix $(BUILD_DIR)/,$(notdir $(UPPER_CASE_ASM_SOURCES:.S=.o)))
+OBJECTS += $(addprefix $(BUILD_DIR)/,$(notdir $(LOWER_CASE_ASM_SOURCES:.s=.o)))
 vpath %.s $(sort $(dir $(ASM_SOURCES)))
 
 $(BUILD_DIR)/%.o: %.cpp STM32Make.make | $(BUILD_DIR) 
@@ -581,6 +587,9 @@ $(BUILD_DIR)/%.o: %.c STM32Make.make | $(BUILD_DIR)
 $(BUILD_DIR)/%.o: %.s STM32Make.make | $(BUILD_DIR)
 	$(AS) -c $(CFLAGS) $< -o $@
 
+$(BUILD_DIR)/%.o: %.S STM32Make.make | $(BUILD_DIR)
+	$(AS) -c $(CFLAGS) $< -o $@
+
 $(BUILD_DIR)/$(TARGET).elf: $(OBJECTS) STM32Make.make
 	$(CXX) $(OBJECTS) $(LDFLAGS) -o $@
 	$(SZ) $@