diff --git a/extra/project-euler/001/001.factor b/extra/project-euler/001/001.factor
index 344b0f1209..1e49be9a60 100644
--- a/extra/project-euler/001/001.factor
+++ b/extra/project-euler/001/001.factor
@@ -46,7 +46,7 @@ PRIVATE>
 
 
 : euler001b ( -- answer )
-    1000 [ dup 5 mod swap 3 mod [ zero? ] either? ] filter sum ;
+    1000 [ [ 5 mod ] [ 3 mod ] bi [ 0 = ] either? ] filter sum ;
 
 ! [ euler001b ] 100 ave-time
 ! 0 ms run / 0 ms GC ave time - 100 trials
diff --git a/extra/project-euler/004/004.factor b/extra/project-euler/004/004.factor
index eb5f97b2de..e1918f5fa6 100644
--- a/extra/project-euler/004/004.factor
+++ b/extra/project-euler/004/004.factor
@@ -21,7 +21,7 @@ IN: project-euler.004
 <PRIVATE
 
 : source-004 ( -- seq )
-    100 999 [a,b] [ 10 mod zero? not ] filter ;
+    100 999 [a,b] [ 10 mod 0 = not ] filter ;
 
 : max-palindrome ( seq -- palindrome )
     natural-sort [ palindrome? ] find-last nip ;
diff --git a/extra/project-euler/014/014.factor b/extra/project-euler/014/014.factor
index 3b812cf242..aa04784151 100644
--- a/extra/project-euler/014/014.factor
+++ b/extra/project-euler/014/014.factor
@@ -58,7 +58,7 @@ PRIVATE>
 <PRIVATE
 
 : worth-calculating? ( n -- ? )
-    1- 3 { [ mod zero? ] [ / even? ] } 2&& ;
+    1- 3 { [ mod 0 = ] [ / even? ] } 2&& ;
 
 PRIVATE>
 
diff --git a/extra/project-euler/019/019.factor b/extra/project-euler/019/019.factor
index 62e2e066ff..16a7139f51 100644
--- a/extra/project-euler/019/019.factor
+++ b/extra/project-euler/019/019.factor
@@ -33,7 +33,7 @@ IN: project-euler.019
 : euler019 ( -- answer )
     1901 2000 [a,b] [
         12 [1,b] [ 1 zeller-congruence ] with map
-    ] map concat [ zero? ] count ;
+    ] map concat [ 0 = ] count ;
 
 ! [ euler019 ] 100 ave-time
 ! 1 ms ave run time - 0.51 SD (100 trials)
@@ -58,7 +58,7 @@ IN: project-euler.019
 PRIVATE>
 
 : euler019a ( -- answer )
-    end-date start-date first-days [ zero? ] count ;
+    end-date start-date first-days [ 0 = ] count ;
 
 ! [ euler019a ] 100 ave-time
 ! 17 ms ave run time - 2.13 SD (100 trials)
diff --git a/extra/project-euler/047/047.factor b/extra/project-euler/047/047.factor
index 84041babb7..30c01d8f61 100644
--- a/extra/project-euler/047/047.factor
+++ b/extra/project-euler/047/047.factor
@@ -66,7 +66,7 @@ SYMBOL: sieve
     0 <repetition> >array sieve set ;
 
 : is-prime? ( index -- ? )
-    sieve get nth zero? ;
+    sieve get nth 0 = ;
 
 : multiples ( n -- seq )
     sieve get length 1- over <range> ;
diff --git a/extra/project-euler/052/052.factor b/extra/project-euler/052/052.factor
index 5362a6e9b0..c382d992f6 100644
--- a/extra/project-euler/052/052.factor
+++ b/extra/project-euler/052/052.factor
@@ -30,7 +30,7 @@ IN: project-euler.052
     [ number>digits natural-sort ] map all-equal? ;
 
 : candidate? ( n -- ? )
-    { [ odd? ] [ 3 mod zero? ] } 1&& ;
+    { [ odd? ] [ 3 mod 0 = ] } 1&& ;
 
 : next-all-same ( x n -- n )
     dup candidate? [
diff --git a/extra/project-euler/common/common.factor b/extra/project-euler/common/common.factor
index d3263bbc1e..8176414153 100644
--- a/extra/project-euler/common/common.factor
+++ b/extra/project-euler/common/common.factor
@@ -42,7 +42,7 @@ IN: project-euler.common
 
 : (sum-divisors) ( n -- sum )
     dup sqrt >fixnum [1,b] [
-        [ 2dup mod zero? [ 2dup / + , ] [ drop ] if ] each
+        [ 2dup mod 0 = [ 2dup / + , ] [ drop ] if ] each
         dup perfect-square? [ sqrt >fixnum neg , ] [ drop ] if
     ] { } make sum ;
 
@@ -68,7 +68,7 @@ PRIVATE>
     ] if ;
 
 : number>digits ( n -- seq )
-    [ dup zero? not ] [ 10 /mod ] [ ] produce reverse nip ;
+    [ dup 0 = not ] [ 10 /mod ] [ ] produce reverse nip ;
 
 : nth-triangle ( n -- n )
     dup 1+ * 2 / ;
@@ -112,7 +112,7 @@ PRIVATE>
     factor-2s dup [ 1+ ]
     [ perfect-square? -1 0 ? ]
     [ dup sqrt >fixnum [1,b] ] tri* [
-        dupd mod zero? [ [ 2 + ] dip ] when
+        dupd mod 0 = [ [ 2 + ] dip ] when
     ] each drop * ;
 
 ! These transforms are for generating primitive Pythagorean triples