diff --git a/changelogs/changelog_2_0_0.md b/changelogs/changelog_2_0_0.md
index 4a15855f4ca27..690258bdc5669 100644
--- a/changelogs/changelog_2_0_0.md
+++ b/changelogs/changelog_2_0_0.md
@@ -44,6 +44,9 @@
 
 - Enabling `-d:nimPreviewCstringConversion`, `ptr char`, `ptr array[N, char]` and `ptr UncheckedArray[N, char]` don't support conversion to cstring anymore.
 
+- Enabling `-d:nimPreviewProcConversion`, `proc` does not support conversion to
+  `pointer`. `cast` may be used instead.
+
 - The `gc:v2` option is removed.
 
 - The `mainmodule` and `m` options are removed.
diff --git a/compiler/nim.cfg b/compiler/nim.cfg
index 5e70c2975e2d1..5b418cfd3b2d8 100644
--- a/compiler/nim.cfg
+++ b/compiler/nim.cfg
@@ -7,6 +7,7 @@ define:nimcore
 define:nimPreviewFloatRoundtrip
 define:nimPreviewSlimSystem
 define:nimPreviewCstringConversion
+define:nimPreviewProcConversion
 define:nimPreviewRangeDefault
 threads:off
 
diff --git a/compiler/sigmatch.nim b/compiler/sigmatch.nim
index 84b99bede61c3..11abc615ccade 100644
--- a/compiler/sigmatch.nim
+++ b/compiler/sigmatch.nim
@@ -1380,7 +1380,10 @@ proc typeRel(c: var TCandidate, f, aOrig: PType,
         result = isEqual
     of tyNil: result = f.allowsNil
     of tyProc:
-      if a.callConv != ccClosure: result = isConvertible
+      if isDefined(c.c.config, "nimPreviewProcConversion"):
+        result = isNone
+      else:
+        if a.callConv != ccClosure: result = isConvertible
     of tyPtr:
       # 'pointer' is NOT compatible to regionized pointers
       # so 'dealloc(regionPtr)' fails:
diff --git a/lib/pure/hashes.nim b/lib/pure/hashes.nim
index 8e5770a71f408..daa7f936612fd 100644
--- a/lib/pure/hashes.nim
+++ b/lib/pure/hashes.nim
@@ -534,7 +534,7 @@ proc hash*[T: tuple | object | proc | iterator {.closure.}](x: T): Hash =
   when T is "closure":
     result = hash((rawProc(x), rawEnv(x)))
   elif T is (proc):
-    result = hash(pointer(x))
+    result = hash(cast[pointer](x))
   else:
     result = 0
     for f in fields(x):
diff --git a/lib/wrappers/openssl.nim b/lib/wrappers/openssl.nim
index fcf52a8d95204..fa72c6c2463e2 100644
--- a/lib/wrappers/openssl.nim
+++ b/lib/wrappers/openssl.nim
@@ -589,7 +589,7 @@ when not useWinVersion and not defined(macosx) and not defined(android) and useN
     if p != nil: deallocShared(p)
 
   proc CRYPTO_malloc_init*() =
-    CRYPTO_set_mem_functions(allocWrapper, reallocWrapper, deallocWrapper)
+    CRYPTO_set_mem_functions(cast[pointer](allocWrapper), cast[pointer](reallocWrapper), cast[pointer](deallocWrapper))
 else:
   proc CRYPTO_malloc_init*() =
     discard
diff --git a/tests/dll/nimhcr_unit.nim b/tests/dll/nimhcr_unit.nim
index 0b924bdf75b06..249f3f9f177ad 100644
--- a/tests/dll/nimhcr_unit.nim
+++ b/tests/dll/nimhcr_unit.nim
@@ -106,14 +106,14 @@ macro carryOutTests(callingConv: untyped): untyped =
       echo `procName`, " implementation #1 ", x
       return x + 1
 
-    let fp1 = cast[F](hcrRegisterProc("dummy_module", `procName`, `p1`))
+    let fp1 = cast[F](hcrRegisterProc("dummy_module", `procName`, cast[pointer](`p1`)))
     echo fp1(10)
 
     proc `p2`(x: int): int {.placeholder.} =
       echo `procName`, " implementation #2 ", x
       return x + 2
 
-    let fp2 = cast[F](hcrRegisterProc("dummy_module", `procName`, `p2`))
+    let fp2 = cast[F](hcrRegisterProc("dummy_module", `procName`, cast[pointer](`p2`)))
     echo fp1(20)
     echo fp2(20)
 
@@ -121,7 +121,7 @@ macro carryOutTests(callingConv: untyped): untyped =
       echo `procName`, " implementation #3 ", x
       return x + 3
 
-    let fp3 = cast[F](hcrRegisterProc("dummy_module", `procName`, `p3`))
+    let fp3 = cast[F](hcrRegisterProc("dummy_module", `procName`, cast[pointer](`p3`)))
     echo fp1(30)
     echo fp2(30)
     echo fp3(30)
diff --git a/tests/stdlib/config.nims b/tests/stdlib/config.nims
index cf97152bab752..dffae2812076d 100644
--- a/tests/stdlib/config.nims
+++ b/tests/stdlib/config.nims
@@ -1,4 +1,5 @@
 switch("styleCheck", "usages")
 switch("styleCheck", "error")
 switch("define", "nimPreviewSlimSystem")
-switch("define", "nimPreviewCstringConversion")
\ No newline at end of file
+switch("define", "nimPreviewCstringConversion")
+switch("define", "nimPreviewProcConversion")
diff --git a/tests/tools/config.nims b/tests/tools/config.nims
index b4bb92b300707..0f0cba8b45300 100644
--- a/tests/tools/config.nims
+++ b/tests/tools/config.nims
@@ -1,2 +1,3 @@
 --d:nimPreviewSlimSystem
---d:nimPreviewCstringConversion
\ No newline at end of file
+--d:nimPreviewCstringConversion
+--d:nimPreviewProcConversion
diff --git a/tests/types/tissues_types.nim b/tests/types/tissues_types.nim
index 7ed0547bfc7e7..275941caec48c 100644
--- a/tests/types/tissues_types.nim
+++ b/tests/types/tissues_types.nim
@@ -44,11 +44,10 @@ block t5648:
     g.bar = 3
 
   var
-    mainPtr1: pointer = main
-    mainPtr2 = pointer(main)
-    mainPtr3 = cast[pointer](main)
+    mainPtr = cast[pointer](main)
+    mainFromPtr = cast[typeof(main)](mainPtr)
 
-  doAssert mainPtr1 == mainPtr2 and mainPtr2 == mainPtr3
+  doAssert main == mainFromPtr
 
   main()