diff --git a/collects/profile/scribblings/analyzer.scrbl b/collects/profile/scribblings/analyzer.scrbl
index 1a22a7d..13cb6eb 100644
--- a/collects/profile/scribblings/analyzer.scrbl
+++ b/collects/profile/scribblings/analyzer.scrbl
@@ -1,7 +1,7 @@
 #lang scribble/doc
 
 @(require scribble/manual
-          (for-label racket/base profile/analyzer))
+          (for-label racket/base racket/contract profile/analyzer))
 
 @title[#:tag "analyzer"]{Analyzing Profile Data}
 
diff --git a/collects/profile/scribblings/renderers.scrbl b/collects/profile/scribblings/renderers.scrbl
index 5f188e5..d56e100 100644
--- a/collects/profile/scribblings/renderers.scrbl
+++ b/collects/profile/scribblings/renderers.scrbl
@@ -2,6 +2,7 @@
 
 @(require scribble/manual
           (for-label racket/base
+                     racket/contract
                      profile/analyzer
                      (prefix-in text: profile/render-text)
                      (prefix-in graphviz: profile/render-graphviz)))
diff --git a/collects/profile/scribblings/sampler.scrbl b/collects/profile/scribblings/sampler.scrbl
index 908521c..511b02d 100644
--- a/collects/profile/scribblings/sampler.scrbl
+++ b/collects/profile/scribblings/sampler.scrbl
@@ -1,7 +1,7 @@
 #lang scribble/doc
 
 @(require scribble/manual
-          (for-label racket/base profile/sampler profile/analyzer))
+          (for-label racket/base racket/contract profile/sampler profile/analyzer))
 
 @title[#:tag "sampler"]{Collecting Profile Information}
 
@@ -9,7 +9,7 @@
 
 @defproc[(create-sampler [to-track (or/c thread? custodian?
                                          (listof (or/c thread? custodian?)))]
-                         [delay nonnegative-number?]
+                         [delay (>=/c 0.0)]
                          [super-cust custodian? (current-custodian)])
          ((symbol?) (any/c) . ->* . any/c)]{
 
diff --git a/collects/profile/scribblings/toplevel.scrbl b/collects/profile/scribblings/toplevel.scrbl
index ec42196..d4dcc3d 100644
--- a/collects/profile/scribblings/toplevel.scrbl
+++ b/collects/profile/scribblings/toplevel.scrbl
@@ -1,7 +1,7 @@
 #lang scribble/doc
 
 @(require scribble/manual
-          (for-label racket/base profile profile/sampler
+          (for-label racket/base racket/contract profile profile/sampler
                      (only-in profile/analyzer analyze-samples profile?)
                      (prefix-in text: profile/render-text)))
 
@@ -16,12 +16,13 @@ intended as a convenient tool for profiling code.
 
 @defproc[(profile-thunk
           [thunk (-> any/c)]
-          [#:delay   delay      nonnegative-number?        0.05]
+          [#:delay   delay      (>=/c 0.0)        0.05]
           [#:repeat  iterations exact-nonnegative-integer? 1]
           [#:threads threads?   any/c                      #f]
           [#:render  renderer   (profile? . -> . any/c)    text:render]
           [#:periodic-renderer periodic-renderer
-           (or/c #f (list/c nonnegative-number? (profile? . -> . any/c)))
+           (or/c #f (list/c (>=/c 0.0)
+                            (profile? . -> . any/c)))
            #f])
          void?]{