The article proposes a somewhat unconventional typology of errors identified on the material of Russian interfering speech of native speakers of the American version of the English language. Linguistics and Language Pedagogy typically classify errors by language levels (phonetic, derivational, lexical, grammatical (morphological and syntactic), including factual and errors that are difficult to interpret), as well as the speaker's reaction to them (notice and unnoticed, corrected and uncorrected errors). The paper presents a typology of errors based on degree of their acceptability for specific groups of speakers ("pardonable" and "unpardonable" errors). The errors made by informants because they are not yet familiar with certain words or rules of the Russian language were recognized as "pardonable": the word with an error is absent from the lexical minimum, and the corresponding requirement is not mentioned in the National Standard. In case the informant is familiar (or has to be familiar) with the rules and vocabulary, but nevertheless makes an error, it was considered "unpardonable". The analysis was carried out on the material of 8 monologues-stories recorded from American students with different levels of Russian language proficiency: 4 monologues received from informants with the basic level (b), and 4 monologues received from informants with the intermediate level (a). The total size of monologues is 1873 words; the total number of errors is 137. As follows from the analysis, overall the informants corrected only 9% of the errors made, and students with a lower level of Russian proficiency (b) corrected their errors more often. The same group of informants is characterized by a larger number of "pardonable" errors. The results of the analysis can be of use for methodological purposes, for compiling study guides and instructions in RFLs, as well as for general linguistics, since they allow to "rank" errors of different types according to their degree of difficulty for different groups of students.