diff --git a/lib/pure/collections/sequtils.nim b/lib/pure/collections/sequtils.nim
index 5b41ea00d0..12b961371d 100644
--- a/lib/pure/collections/sequtils.nim
+++ b/lib/pure/collections/sequtils.nim
@@ -84,6 +84,11 @@ import std/private/since
 
 import macros
 
+when defined(nimHasEffectsOf):
+  {.experimental: "strictEffects".}
+else:
+  {.pragma: effectsOf.}
+
 macro evalOnceAs(expAlias, exp: untyped,
                  letAssigneable: static[bool]): untyped =
   ## Injects `expAlias` in caller scope, to avoid bugs involving multiple
@@ -356,7 +361,7 @@ func distribute*[T](s: seq[T], num: Positive, spread = true): seq[seq[T]] =
       first = last
 
 proc map*[T, S](s: openArray[T], op: proc (x: T): S {.closure.}):
-                                                            seq[S]{.inline.} =
+                                                            seq[S] {.inline, effectsOf: op.} =
   ## Returns a new sequence with the results of the `op` proc applied to every
   ## item in the container `s`.
   ##
@@ -382,7 +387,7 @@ proc map*[T, S](s: openArray[T], op: proc (x: T): S {.closure.}):
     result[i] = op(s[i])
 
 proc apply*[T](s: var openArray[T], op: proc (x: var T) {.closure.})
-                                                              {.inline.} =
+                                                              {.inline, effectsOf: op.} =
   ## Applies `op` to every item in `s`, modifying it directly.
   ##
   ## Note that the container `s` must be declared as a `var`,
@@ -401,7 +406,7 @@ proc apply*[T](s: var openArray[T], op: proc (x: var T) {.closure.})
   for i in 0 ..< s.len: op(s[i])
 
 proc apply*[T](s: var openArray[T], op: proc (x: T): T {.closure.})
-                                                              {.inline.} =
+                                                              {.inline, effectsOf: op.} =
   ## Applies `op` to every item in `s` modifying it directly.
   ##
   ## Note that the container `s` must be declared as a `var`
@@ -420,7 +425,7 @@ proc apply*[T](s: var openArray[T], op: proc (x: T): T {.closure.})
 
   for i in 0 ..< s.len: s[i] = op(s[i])
 
-proc apply*[T](s: openArray[T], op: proc (x: T) {.closure.}) {.inline, since: (1, 3).} =
+proc apply*[T](s: openArray[T], op: proc (x: T) {.closure.}) {.inline, since: (1, 3), effectsOf: op.} =
   ## Same as `apply` but for a proc that does not return anything
   ## and does not mutate `s` directly.
   runnableExamples:
@@ -429,7 +434,7 @@ proc apply*[T](s: openArray[T], op: proc (x: T) {.closure.}) {.inline, since: (1
     assert message == "01234"
   for i in 0 ..< s.len: op(s[i])
 
-iterator filter*[T](s: openArray[T], pred: proc(x: T): bool {.closure.}): T =
+iterator filter*[T](s: openArray[T], pred: proc(x: T): bool {.closure.}): T {.effectsOf: pred.} =
   ## Iterates through a container `s` and yields every item that fulfills the
   ## predicate `pred` (a function that returns a `bool`).
   ##
@@ -453,7 +458,7 @@ iterator filter*[T](s: openArray[T], pred: proc(x: T): bool {.closure.}): T =
       yield s[i]
 
 proc filter*[T](s: openArray[T], pred: proc(x: T): bool {.closure.}): seq[T]
-                                                                  {.inline.} =
+                                                                  {.inline, effectsOf: pred.} =
   ## Returns a new sequence with all the items of `s` that fulfill the
   ## predicate `pred` (a function that returns a `bool`).
   ##
@@ -480,7 +485,7 @@ proc filter*[T](s: openArray[T], pred: proc(x: T): bool {.closure.}): seq[T]
       result.add(s[i])
 
 proc keepIf*[T](s: var seq[T], pred: proc(x: T): bool {.closure.})
-                                                                {.inline.} =
+                                                                {.inline, effectsOf: pred.} =
   ## Keeps the items in the passed sequence `s` if they fulfill the
   ## predicate `pred` (a function that returns a `bool`).
   ##
@@ -685,7 +690,7 @@ since (1, 1):
       if pred: result += 1
     result
 
-proc all*[T](s: openArray[T], pred: proc(x: T): bool {.closure.}): bool =
+proc all*[T](s: openArray[T], pred: proc(x: T): bool {.closure.}): bool {.effectsOf: pred.} =
   ## Iterates through a container and checks if every item fulfills the
   ## predicate.
   ##
@@ -727,7 +732,7 @@ template allIt*(s, pred: untyped): bool =
       break
   result
 
-proc any*[T](s: openArray[T], pred: proc(x: T): bool {.closure.}): bool =
+proc any*[T](s: openArray[T], pred: proc(x: T): bool {.closure.}): bool {.effectsOf: pred.} =
   ## Iterates through a container and checks if at least one item
   ## fulfills the predicate.
   ##
diff --git a/tests/stdlib/tsequtils.nim b/tests/stdlib/tsequtils.nim
index 6c9c928736..3384734071 100644
--- a/tests/stdlib/tsequtils.nim
+++ b/tests/stdlib/tsequtils.nim
@@ -8,6 +8,9 @@ import std/sequtils
 import strutils
 from algorithm import sorted
 
+{.experimental: "strictEffects".}
+{.push warningAsError[Effect]: on.}
+
 # helper for testing double substitution side effects which are handled
 # by `evalOnceAs`
 var counter = 0
@@ -507,3 +510,5 @@ template main =
 
 static: main()
 main()
+
+{.pop.}