diff --git a/src/iec61850/client/client_goose_control.c b/src/iec61850/client/client_goose_control.c
index 467af2d2..331efae4 100644
--- a/src/iec61850/client/client_goose_control.c
+++ b/src/iec61850/client/client_goose_control.c
@@ -213,7 +213,7 @@ ClientGooseControlBlock_getDstAddress(ClientGooseControlBlock self)
         goto exit_error;
     }
 
-    uint8_t* addrBuf = MmsValue_getOctetStringBuffer(addr);
+    const uint8_t* addrBuf = MmsValue_getOctetStringBuffer(addr);
 
     memcpy(&(retVal.dstAddress), addrBuf, 6);
 
diff --git a/src/iec61850/client/client_sv_control.c b/src/iec61850/client/client_sv_control.c
index 5b9c235a..32255ef1 100644
--- a/src/iec61850/client/client_sv_control.c
+++ b/src/iec61850/client/client_sv_control.c
@@ -312,7 +312,7 @@ ClientSVControlBlock_getDstAddress(ClientSVControlBlock self)
         goto exit_cleanup;
     }
 
-    uint8_t* addrBuf = MmsValue_getOctetStringBuffer(addr);
+    const uint8_t* addrBuf = MmsValue_getOctetStringBuffer(addr);
 
     memcpy(&(retVal.dstAddress), addrBuf, 6);
 
diff --git a/src/iec61850/inc/iec61850_server.h b/src/iec61850/inc/iec61850_server.h
index 2a7d6f2f..72cd322d 100644
--- a/src/iec61850/inc/iec61850_server.h
+++ b/src/iec61850/inc/iec61850_server.h
@@ -1375,7 +1375,7 @@ ControlAction_getOrCat(ControlAction self);
  *
  * \return the originator identifier
  */
-LIB61850_API uint8_t*
+LIB61850_API const uint8_t*
 ControlAction_getOrIdent(ControlAction self, int* orIdentSize);
 
 /**
diff --git a/src/iec61850/server/mms_mapping/control.c b/src/iec61850/server/mms_mapping/control.c
index bcbb7d22..56f345cf 100644
--- a/src/iec61850/server/mms_mapping/control.c
+++ b/src/iec61850/server/mms_mapping/control.c
@@ -2467,7 +2467,7 @@ ControlAction_getOrCat(ControlAction self)
     return 0;
 }
 
-uint8_t*
+const uint8_t*
 ControlAction_getOrIdent(ControlAction self, int* orIdentSize)
 {
     ControlObject* controlObject = (ControlObject*) self;
diff --git a/src/iec61850/server/mms_mapping/reporting.c b/src/iec61850/server/mms_mapping/reporting.c
index 9e37cee3..e90ca4c2 100644
--- a/src/iec61850/server/mms_mapping/reporting.c
+++ b/src/iec61850/server/mms_mapping/reporting.c
@@ -1587,7 +1587,7 @@ updateOwner(ReportControl* rc, MmsServerConnection connection)
 static bool
 checkForZeroEntryID(MmsValue* value)
 {
-    uint8_t* buffer = MmsValue_getOctetStringBuffer(value);
+    const uint8_t* buffer = MmsValue_getOctetStringBuffer(value);
 
     int i = 0;
 
diff --git a/src/mms/inc/mms_value.h b/src/mms/inc/mms_value.h
index 206345c4..bc4fbdb7 100644
--- a/src/mms/inc/mms_value.h
+++ b/src/mms/inc/mms_value.h
@@ -300,7 +300,7 @@ MmsValue_getBoolean(const MmsValue* value);
  * \returns the string value as 0 terminated C string
  */
 LIB61850_API const char*
-MmsValue_toString(MmsValue* self);
+MmsValue_toString(const MmsValue* self);
 
 /**
  * \brief Returns the (maximum) length of the string
@@ -310,7 +310,7 @@ MmsValue_toString(MmsValue* self);
  * \param self MmsValue instance to operate on. Has to be of a type MMS_VISIBLE_STRING or MMS_STRING.
  */
 LIB61850_API int
-MmsValue_getStringSize(MmsValue* self);
+MmsValue_getStringSize(const MmsValue* self);
 
 LIB61850_API void
 MmsValue_setVisibleString(MmsValue* self, const char* string);
@@ -463,8 +463,8 @@ MmsValue_setUtcTimeByBuffer(MmsValue* self, const uint8_t* buffer);
  *
  * \return the buffer containing the raw data
  */
-LIB61850_API uint8_t*
-MmsValue_getUtcTimeBuffer(MmsValue* self);
+LIB61850_API const uint8_t*
+MmsValue_getUtcTimeBuffer(const MmsValue* self);
 
 /**
  * \brief Get a millisecond time value from an MmsValue object of MMS_UTCTIME type.
@@ -611,7 +611,7 @@ MmsValue_getOctetStringSize(const MmsValue* self);
  * \return maximum size in bytes
  */
 LIB61850_API uint16_t
-MmsValue_getOctetStringMaxSize(MmsValue* self);
+MmsValue_getOctetStringMaxSize(const MmsValue* self);
 
 /**
  * \brief Returns the reference to the internally hold buffer of an MmsValue object of type MMS_OCTET_STRING.
@@ -622,8 +622,8 @@ MmsValue_getOctetStringMaxSize(MmsValue* self);
  *
  * \return reference to the buffer
  */
-LIB61850_API uint8_t*
-MmsValue_getOctetStringBuffer(MmsValue* self);
+LIB61850_API const uint8_t*
+MmsValue_getOctetStringBuffer(const MmsValue* self);
 
 /**
  * \brief Get the value of a single octet of an MmsType object of type MMS_OCTET_STRING
@@ -637,7 +637,7 @@ MmsValue_getOctetStringBuffer(MmsValue* self);
  * \return the value of the octet (0 to 255, or 0x00 to 0xFF)
  */
 LIB61850_API uint8_t
-MmsValue_getOctetStringOctet(MmsValue* self, int octetPos);
+MmsValue_getOctetStringOctet(const MmsValue* self, int octetPos);
 
 /**
  * \brief Update the value of an MmsValue instance by the value of another MmsValue instance.
@@ -956,7 +956,7 @@ MmsValue_setDeletableRecursive(MmsValue* value);
  * \return 1 if deletable flag is set, otherwise 0
  */
 LIB61850_API int
-MmsValue_isDeletable(MmsValue* self);
+MmsValue_isDeletable(const MmsValue* self);
 
 /**
  * \brief Get the MmsType of an MmsValue instance
@@ -985,8 +985,8 @@ MmsValue_getSubElement(MmsValue* self, MmsVariableSpecification* varSpec, char*
  *
  * \return the value type as a human readable string
  */
-LIB61850_API char*
-MmsValue_getTypeString(MmsValue* self);
+LIB61850_API const char*
+MmsValue_getTypeString(const MmsValue* self);
 
 /**
  * \brief create a string representation of the MmsValue object in the provided buffer
@@ -1040,7 +1040,7 @@ MmsValue_encodeMmsData(MmsValue* self, uint8_t* buffer, int bufPos, bool encode)
  * \return the maximum encoded size in bytes of the MMS data element
  */
 LIB61850_API int
-MmsValue_getMaxEncodedSize(MmsValue* self);
+MmsValue_getMaxEncodedSize(const MmsValue* self);
 
 /**
  * \brief Calculate the maximum encoded size of a variable of this type
diff --git a/src/mms/iso_mms/common/mms_value.c b/src/mms/iso_mms/common/mms_value.c
index 549619a8..f1d06fe9 100644
--- a/src/mms/iso_mms/common/mms_value.c
+++ b/src/mms/iso_mms/common/mms_value.c
@@ -830,8 +830,8 @@ MmsValue_setUtcTimeByBuffer(MmsValue* self, const uint8_t* buffer)
     }
 }
 
-uint8_t*
-MmsValue_getUtcTimeBuffer(MmsValue* self)
+const uint8_t*
+MmsValue_getUtcTimeBuffer(const MmsValue* self)
 {
     return self->value.utcTime;
 }
@@ -1506,19 +1506,19 @@ MmsValue_getOctetStringSize(const MmsValue* self)
 }
 
 uint16_t
-MmsValue_getOctetStringMaxSize(MmsValue* self)
+MmsValue_getOctetStringMaxSize(const MmsValue* self)
 {
     return abs(self->value.octetString.maxSize);
 }
 
-uint8_t*
-MmsValue_getOctetStringBuffer(MmsValue* self)
+const uint8_t*
+MmsValue_getOctetStringBuffer(const MmsValue* self)
 {
     return self->value.octetString.buf;
 }
 
 uint8_t
-MmsValue_getOctetStringOctet(MmsValue* self, int octetPos)
+MmsValue_getOctetStringOctet(const MmsValue* self, int octetPos)
 {
     uint8_t octet = 0x00; /* default value, for out of range request */
 
@@ -1936,7 +1936,7 @@ MmsValue_setVisibleString(MmsValue* self, const char* string)
 }
 
 const char*
-MmsValue_toString(MmsValue* self)
+MmsValue_toString(const MmsValue* self)
 {
     if ((self->type == MMS_VISIBLE_STRING) || (self->type == MMS_STRING))
         return self->value.visibleString.buf;
@@ -1945,7 +1945,7 @@ MmsValue_toString(MmsValue* self)
 }
 
 int
-MmsValue_getStringSize(MmsValue* self)
+MmsValue_getStringSize(const MmsValue* self)
 {
     if ((self->type == MMS_VISIBLE_STRING) || (self->type == MMS_STRING))
         return self->value.visibleString.size;
@@ -2117,7 +2117,7 @@ MmsValue_setDeletableRecursive(MmsValue* self)
 }
 
 int
-MmsValue_isDeletable(MmsValue* self)
+MmsValue_isDeletable(const MmsValue* self)
 {
     return self->deleteValue;
 }
@@ -2134,8 +2134,8 @@ MmsValue_getSubElement(MmsValue* self, MmsVariableSpecification* varSpec, char*
     return MmsVariableSpecification_getChildValue(varSpec, self, mmsPath);
 }
 
-char*
-MmsValue_getTypeString(MmsValue* self)
+const char*
+MmsValue_getTypeString(const MmsValue* self)
 {
     switch (MmsValue_getType(self))
     {
diff --git a/src/mms/iso_mms/server/mms_access_result.c b/src/mms/iso_mms/server/mms_access_result.c
index b17461f0..19ee31d9 100644
--- a/src/mms/iso_mms/server/mms_access_result.c
+++ b/src/mms/iso_mms/server/mms_access_result.c
@@ -335,7 +335,7 @@ exit_with_error:
 }
 
 static int
-MmsValue_getMaxStructSize(MmsValue* self)
+MmsValue_getMaxStructSize(const MmsValue* self)
 {
     int componentsSize = 0;
     int i;
@@ -354,7 +354,7 @@ MmsValue_getMaxStructSize(MmsValue* self)
 }
 
 int
-MmsValue_getMaxEncodedSize(MmsValue* self)
+MmsValue_getMaxEncodedSize(const MmsValue* self)
 {
     int size = 0;
     int elementSize = 0;