diff --git a/src/tokens.h b/src/tokens.h
index cca47e1..0b02c90 100644
--- a/src/tokens.h
+++ b/src/tokens.h
@@ -15,6 +15,9 @@
 *  limitations under the License.
 ********************************************************************************/
 
+#ifndef _TOKENS_H_
+#define _TOKENS_H_
+
 #include "os.h"
 
 typedef struct tokenDefinition_t {
@@ -66,3 +69,5 @@ extern tokenDefinition_t const TOKENS_GOCHAIN[NUM_TOKENS_GOCHAIN];
 extern tokenDefinition_t const TOKENS_MIX[NUM_TOKENS_MIX];
 extern tokenDefinition_t const TOKENS_REOSC[NUM_TOKENS_REOSC];
 extern tokenDefinition_t const TOKENS_HPB[NUM_TOKENS_HPB];
+
+#endif /* _TOKENS_H_ */
diff --git a/src_common/ethUstream.h b/src_common/ethUstream.h
index 1f708da..d134034 100644
--- a/src_common/ethUstream.h
+++ b/src_common/ethUstream.h
@@ -15,6 +15,9 @@
 *  limitations under the License.
 ********************************************************************************/
 
+#ifndef _ETHUSTREAM_H_
+#define _ETHUSTREAM_H_
+
 #include "os.h"
 #include "cx.h"
 #include <stdbool.h>
@@ -96,3 +99,5 @@ parserStatus_e processTx(txContext_t *context, uint8_t *buffer,
 parserStatus_e continueTx(txContext_t *context);
 void copyTxData(txContext_t *context, uint8_t *out, uint32_t length);
 uint8_t readTxByte(txContext_t *context);
+
+#endif /* _ETHUSTREAM_H_ */
\ No newline at end of file
diff --git a/src_common/ethUtils.h b/src_common/ethUtils.h
index b716938..fd8b0da 100644
--- a/src_common/ethUtils.h
+++ b/src_common/ethUtils.h
@@ -15,6 +15,9 @@
 *  limitations under the License.
 ********************************************************************************/
 
+#ifndef _ETHUTILS_H_
+#define _ETHUTILS_H_
+
 #include "os.h"
 #include "cx.h"
 
@@ -46,3 +49,5 @@ void getEthAddressStringFromBinary(uint8_t *address, uint8_t *out,
 
 bool adjustDecimals(char *src, uint32_t srcLength, char *target,
                     uint32_t targetLength, uint8_t decimals);
+
+#endif /* _ETHUTILS_H_ */
\ No newline at end of file
diff --git a/src_common/uint256.h b/src_common/uint256.h
index 39daa50..1d213ec 100644
--- a/src_common/uint256.h
+++ b/src_common/uint256.h
@@ -17,6 +17,9 @@
 
 // Adapted from https://github.com/calccrypto/uint256_t
 
+#ifndef _UINT256_H_
+#define _UINT256_H_
+
 #include <stdint.h>
 #include <stdbool.h>
 
@@ -63,3 +66,5 @@ bool tostring128(uint128_t *number, uint32_t base, char *out,
                  uint32_t outLength);
 bool tostring256(uint256_t *number, uint32_t base, char *out,
                  uint32_t outLength);
+
+#endif /* _UINT256_H_ */
\ No newline at end of file