diff --git a/src/lib/openjp2/j2k.c b/src/lib/openjp2/j2k.c
index 2d955f9a..a2521ebb 100644
--- a/src/lib/openjp2/j2k.c
+++ b/src/lib/openjp2/j2k.c
@@ -1305,7 +1305,7 @@ typedef struct j2k_prog_order {
     char str_prog[5];
 } j2k_prog_order_t;
 
-static j2k_prog_order_t j2k_prog_order_list[] = {
+static const j2k_prog_order_t j2k_prog_order_list[] = {
     {OPJ_CPRL, "CPRL"},
     {OPJ_LRCP, "LRCP"},
     {OPJ_PCRL, "PCRL"},
@@ -1602,9 +1602,9 @@ static void  opj_j2k_write_float_to_float64(const void * p_src_data,
     }
 }
 
-char *opj_j2k_convert_progression_order(OPJ_PROG_ORDER prg_order)
+const char *opj_j2k_convert_progression_order(OPJ_PROG_ORDER prg_order)
 {
-    j2k_prog_order_t *po;
+    const j2k_prog_order_t *po;
     for (po = j2k_prog_order_list; po->enum_prog != -1; po++) {
         if (po->enum_prog == prg_order) {
             return po->str_prog;
diff --git a/src/lib/openjp2/j2k.h b/src/lib/openjp2/j2k.h
index d61c96db..c9308f7d 100644
--- a/src/lib/openjp2/j2k.h
+++ b/src/lib/openjp2/j2k.h
@@ -617,7 +617,7 @@ OPJ_BOOL opj_j2k_setup_encoder(opj_j2k_t *p_j2k,
 /**
 Converts an enum type progression order to string type
 */
-char *opj_j2k_convert_progression_order(OPJ_PROG_ORDER prg_order);
+const char *opj_j2k_convert_progression_order(OPJ_PROG_ORDER prg_order);
 
 /* ----------------------------------------------------------------------- */
 /*@}*/
diff --git a/src/lib/openjp2/mqc.c b/src/lib/openjp2/mqc.c
index 8f69e29e..6299b171 100644
--- a/src/lib/openjp2/mqc.c
+++ b/src/lib/openjp2/mqc.c
@@ -79,7 +79,7 @@ static void opj_mqc_setbits(opj_mqc_t *mqc);
 /* <summary> */
 /* This array defines all the possible states for a context. */
 /* </summary> */
-static opj_mqc_state_t mqc_states[47 * 2] = {
+static const opj_mqc_state_t mqc_states[47 * 2] = {
     {0x5601, 0, &mqc_states[2], &mqc_states[3]},
     {0x5601, 1, &mqc_states[3], &mqc_states[2]},
     {0x3401, 0, &mqc_states[4], &mqc_states[12]},
diff --git a/src/lib/openjp2/mqc.h b/src/lib/openjp2/mqc.h
index ac3aff10..69a2a79d 100644
--- a/src/lib/openjp2/mqc.h
+++ b/src/lib/openjp2/mqc.h
@@ -61,9 +61,9 @@ typedef struct opj_mqc_state {
     /** the Most Probable Symbol (0 or 1) */
     OPJ_UINT32 mps;
     /** next state if the next encoded symbol is the MPS */
-    struct opj_mqc_state *nmps;
+    const struct opj_mqc_state *nmps;
     /** next state if the next encoded symbol is the LPS */
-    struct opj_mqc_state *nlps;
+    const struct opj_mqc_state *nlps;
 } opj_mqc_state_t;
 
 #define MQC_NUMCTXS 19
@@ -87,9 +87,9 @@ typedef struct opj_mqc {
     /** pointer to the end of the buffer */
     OPJ_BYTE *end;
     /** Array of contexts */
-    opj_mqc_state_t *ctxs[MQC_NUMCTXS];
+    const opj_mqc_state_t *ctxs[MQC_NUMCTXS];
     /** Active context */
-    opj_mqc_state_t **curctx;
+    const opj_mqc_state_t **curctx;
     /* lut_ctxno_zc shifted by (1 << 9) * bandno */
     const OPJ_BYTE* lut_ctxno_zc_orient;
     /** Original value of the 2 bytes at end[0] and end[1] */
diff --git a/src/lib/openjp2/mqc_inl.h b/src/lib/openjp2/mqc_inl.h
index d95d9492..310a3287 100644
--- a/src/lib/openjp2/mqc_inl.h
+++ b/src/lib/openjp2/mqc_inl.h
@@ -157,7 +157,7 @@ static INLINE OPJ_UINT32 opj_mqc_raw_decode(opj_mqc_t *mqc)
 }
 
 #define DOWNLOAD_MQC_VARIABLES(mqc, curctx, c, a, ct) \
-        register opj_mqc_state_t **curctx = mqc->curctx; \
+        register const opj_mqc_state_t **curctx = mqc->curctx; \
         register OPJ_UINT32 c = mqc->c; \
         register OPJ_UINT32 a = mqc->a; \
         register OPJ_UINT32 ct = mqc->ct